Synthetic peptides having pituitary growth hormone releasing activity

ABSTRACT

Novel peptides having the following amino acid sequence ##STR1## wherein X 1 , X 2 , and X 3  are selected from a group consisting of N-terminal and desamino alpha-carbon substitutions and a and b are 0 or 1, provided that a and b are always 0 when A 1  is a desamino residue; A 1  and A 4  are selected from a group consisting of histidyl, arginyl, lysyl, α-naphthylalanyl, β-naphthylalanyl, isoquinolyl, tyrosyl, tryptophyl, phenylalanyl, homologues and analogues thereof, and, with respect to A 1  only the desamino forms thereof; A 2  and A 5  are selected from a group consisting of D-histidyl, D-arginyl, D-lysyl, D-α-naphthylalanyl, D-β-naphthylalanyl, D-isoquinolyl, D-tyrosyl, D-tryptophyl, D-phenylalanyl, homologues and analogues thereof; A 3  is selected from a group consisting of glycyl, alanyl, valyl, leucyl, isoleucyl, prolyl, seryl, threonyl, methionyl, aspartyl, glutamyl, asparginyl, glutaminyl, histidyl, D-alanyl, D-valyl, D-leucyl, D-isoleucyl, D-prolyl, D-seryl, D-threonyl, D-methionyl, D-aspartyl, D-glutamyl, D-asparaginyl, D-glutaminyl, D-histidyl, and homologues and analogues thereof; A 6  is selected from a group consisting of amino acids of the L- and D- configuration, homologues and analogues thereof, and the descarboxy forms thereof; and Y is selected from a group consisting of C-terminal and descarboxy alpha-carbon substitutions; and the pharmaceutically acceptable salts thereof.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of application Ser. No. 254,035, filed Apr. 14, 1981, now abandoned; which application is a continuation of application Ser. No. 165,163, filed July 1, 1980, now abandoned; which application is a continuation-in-part of application Ser. No. 085,824, filed Oct. 17, 1979, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to peptides which possess pituitary growth hormone releasing activity.

2. Description of the Prior Art

Growth hormone, which is secreted from the pituitary, causes growth of all tissues of the body that are capable of growing. In addition, growth hormone is known to have the following basic effects on the metabolic process of the body:

1. Increased rate of protein synthesis in all cells of the body;

2. Decreased rate of carbohydrate utilization in cells of the body;

3. Increased mobilization of free fatty acids and use of fatty acids for energy.

A deficiency in growth hormone secretion can result in various medical disorders, such as some instances of dwarfism.

Various ways are known to release growth hormone. For example, chemicals such as arginine, L-3,4-dihydroxyphenylalanine (L-DOPA), glucagon, vasopressin, and insulin induced hypoglycemia, as well as activities such as sleep and exercise, indirectly cause growth hormone to be released from the pituitary by acting in some fashion on the hypothalmus perhaps either to decrease somatostatin secretion or to increase an unknown endogenous growth hormone-releasing hormone or both.

Compounds which directly act on the pituitary to release growth hormone include prostaglandin E₁ and E₂, theophylline, and cyclic nucleotides. However, these compounds neither specifically release growth hormone nor are they believed to act at the putative growth hormone-releasing hormone receptors in the peripheral membrane of the pituitary cell to initiate growth hormone release.

In addition, under special conditions certain chemically defined peptides, e.g., vasopressin, thyroid-releasing hormone (TRH), luteinizing hormone-releasing hormone (LH-RH), α-melanocyte-stiumulating hormone (α-MSH), glucagon, substance P, neurotensin; Met-enkephalin, β-endorphin, cholera-enderotoxin, and basic myelin protein, act to release growth hormone from the pituitary. However, only TRH acts directly on the pituitary to elicit this response. Furthermore, the above listed peptides release other pituitary hormones and under most experimental conditions do not release growth hormone. For example, TRH does not release growth hormone in normal rats or in normal humans or from pituitaries of normal rats or monkeys. In vitro, TRH releases growth hormone, prolactin, and thyroid stimulating hormone (TSH) in certain species, and, in vivo, TRH releases these hormones from bovine pituitary.

Vasopressin's induced release of growth hormone is considered to be due to a non-specific response to stress caused by administration of high dosages of vasopressin.

Accordingly it would be highly desirable to have a compound which directly acts on the pituitary under normal experimental conditions to effect the release of growth hormone therefrom. Such peptides would be useful in vitro, e.g., as unique research tools for understanding how growth hormone secretion is regulated at the pituitary level and would also be useful in vivo, e.g., to treat symptoms related to growth hormone deficiencies, to increase the rate and extent of growth in commercial animals, to increase milk yield in commercial animals, and to reduce the number of mucosal erosions induced by hypoxemia.

SUMMARY OF THE INVENTION

In accordance with the present invention there is provided peptides which act directly on the pituitary under normal experimental conditions in vitro to release growth hormone therefrom.

These growth hormone releasing peptides can be utilized in vitro as unique research tools for understanding, inter alia, how growth hormone secretion is regulated at the pituitary level.

Also, the growth hormone releasing peptides of the instant invention can also be administered in vivo to increase growth hormone release.

More particularly, this invention encompasses novel peptide having the formula I ##STR2## wherein X₁, X₂, and X₃ are selected from a group consisting of N-terminal and desamino alpha-carbon substitutions; a and b are 0 or 1, provided that a and b are always 0 when A₁ is a desamino residue; A₁ and A₄ are selected from a group consisting of histidyl, arginyl, lysyl, α-naphthylalanyl, β-naphthylalanyl, isoquinolyl, tyrosyl, tryptophyl, phenylalanyl, homologues and analogues thereof, and, with respect to A₁ only, the desamino forms thereof; A₂ and A₅ are selected from a group consisting of D-histidyl, D-arginyl, D-lysyl, D-α-naphthylalanyl, D-β-naphthylalanyl, D-isoquinolyl, D-tyrosyl, D-tryptophyl, D-phenylalanyl, homologues and analogues thereof, and, with respect to A₅ only, the descarboxy forms thereof; A₃ is selected from a group consisting of glycyl, alanyl, valyl, leucyl, isoleucyl, prolyl, seryl, threonyl, methionyl, aspartyl, glutamyl, asparaginyl, glutaminyl, histidyl, D-alanyl, D-valyl, D-leucyl, D-isoleucyl, D-prolyl, D-seryl, D-threonyl, D-methionyl, D-aspartyl, D-glutamyl, D-asparaginyl, D-glutaminyl, D-histidyl, and homologues and analogues thereof; A₆ is selected from a group consisting of amino acids of the L- and D-configuration, homologues and analogues thereof, and the descarboxy forms thereof; and Y is selected from a group consisting of C-terminal and descarboxy alpha-carbon substitutions; and the pharmaceutically acceptable salts thereof.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The peptides of this invention have the amino acid residue sequence represented by formula I, supra.

All amino acid residues identified herein are in the natural or L-configuration unless otherwise specified.

Abbreviations for amino acid residues are used in accordance with the following standard peptide nomenclature:

    ______________________________________                                         Tyr     L-tyrosyl     Ile       L-isoleucyl                                    D-Tyr   D-tyrosyl     D-Ile     D-isoleucyl                                    Gly     glycyl        Leu       L-leucyl                                       Phe     L-phenylalanyl                                                                               D-Leu     D-leucyl                                       D-Phe   D-phenylalanyl                                                                               Thr       L-threonyl                                     Met     L-methionyl   D-Thr     D-threonyl                                     D-Met   D-methionyl   Val       L-valyl                                        Ala     L-alanyl      D-Val     D-valyl                                        D-Ala   D-alanyl      Pro       L-prolyl                                       Ser     L-seryl       D-Pro     D-prolyl                                       D-Ser   D-seryl       Gln       L-glutaminyl                                   Lys     L-lysyl       D-Gln     D-glutaminyl                                   D-Lys   D-lysyl       Glu       L-glutamyl                                     Asn     L-asparaginyl D-Glu     D-glutamyl                                     D-Asn   D-asparaginyl Trp       L-tryptophyl                                   His     L-histidyl    D-trp     D-tryptophyl                                                         L-Asp     L-aspartyl                                     D-His   D-histidyl    D-Asp     D-aspartyl                                     Cys     L-cysteinyl   Arg       L-arginyl                                      D-Cys   D-cysteinyl   D-Arg     D-arginyl                                      Hypro   L-hydroxyprolyl                                                        D-Hypro D-hydroxyprolyl                                                        Dopa    L-3,4-dihydroxy-                                                               phenylalanyl  L-<Glu    L-pyroglutamyl                                 D-Dopa  D-3,4-dihydroxy-                                                               phenylalanyl  D-<Glu    D-pyroglutamyl                                 Hylys   L-δ-hydroxylysyl                                                                       Sar       N--methylglycyl                                                                (sarcosyl)                                     D-Hylys D-δ-hydroxylysyl                                                 Aib     L-α-methylalanyl                                                                       α-Naphth                                                                           L-α-naphthyl-                                    (L-aminoisobutyryl)     alanyl                                                               D-α-                                                                               D-α-naphthyl-                                                  Naphth    alanyl                                                               β-Naphth                                                                            L-β-naphthyl-                                                             alanyl                                         Iql     L-isoquinolyl D-β- D-β-naphthyl-                             D-Iql   D-isoquinolyl Naphth    alanyl                                         ______________________________________                                    

Virtually any suitable N-terminal and desamino alpha-carbon substitution can be used in the instant invention as represented by the various structural formulas set forth herein. Typical N-terminal and desamino alpha-carbon substituions include, but are not limited to, those also set forth in Table I.

                  TABLE I                                                          ______________________________________                                         NTerminus and Desamino Alpha-Carbon Substitutions.sup.1                        X.sub.1      X.sub.2 X.sub.3     a   b                                         ______________________________________                                         NTerminus Substitutions                                                        R.sub.1      R.sub.2 --          1   0                                         R.sub.1      R.sub.2 R.sub.3     1   1                                          ##STR3##    R.sub.2 --          1   0                                          ##STR4##    R.sub.2 --          1   0                                         R.sub.1      HO      --          1   0                                          ##STR5##    R.sub.3 --          1   0                                          ##STR6##    R.sub.3 --          1   0                                         Desamino Alpha-Carbon Substitutions                                            R            --      --          0   0                                         RZ           --      --          0   0                                         ______________________________________                                          .sup.1 LEGEND: R, R.sub.1, R.sub.2, and R.sub.3 are selected from a group      consisting of hydrogen; straight and branched chain lower alkyl groups         having from 1 to 6 carbon atoms; cycloalkyl groups having from 3 to 6          carbon atoms; benzyl; benzhydryl; trityl; aryl; alkoxybenzyl;                  alkoxybenzhydryl; alkoxytrityl; lower haloalkyl groups having from 1 to 6      carbon atoms; halobenzyl; halobenzhydryl; halotrityl; haloaryl; and            cyclohaloalkyl groups having from 3 to 6 carbon atoms. Preferably, R,          R.sub.1, R.sub.2, and R.sub.3 are selected from the group consisting of        hydrogen and alkyl groups having from 1 to 6 carbon atoms. More                preferably, R, R.sub.1, R.sub.2, and R.sub.3 are selected from the group       consisting of hydrogen and alkyl groups having 1 to 2 carbon atoms.            Z is selected from a group consisting of oxygen and sulfur. Z is               preferably oxygen.                                                       

Virtually any suitable C-terminal and descarboxy alpha-carbon substitution can be used in the instant invention as represented by the various structural formulas set forth herein. Typical C-terminal and descarboxy alpha-carbon substitutions include, but are not limited to, those also set forth in Table II.

                  TABLE II                                                         ______________________________________                                         CTerminus and Descarboxy                                                       Alpha-Carbon Substitutions.sup.1                                               ______________________________________                                         CTerminus Substitutions                                                        OR                                                                              ##STR7##                                                                       ##STR8##                                                                       ##STR9##                                                                       ##STR10##                                                                     Descarboxy Alpha-Carbon Substitutions                                          R                                                                               ##STR11##                                                                      ##STR12##                                                                      ##STR13##                                                                      ##STR14##                                                                      ##STR15##                                                                      ##STR16##                                                                     ______________________________________                                          .sup.1 LEGEND: R, R.sub.1, R.sub.2, and R.sub. 3 are as defined in Table       I, supra.                                                                      V is selected from a group consisting of oxygen, sulfur, and nitrogen. V       is preferably oxygen.                                                    

The structure of amino acid residues employed in the peptides of this invention are set forth in Table III. Typical homologues and analogues of these amino acid residues which can also be employed in the peptides of this invention include, but are not limited to, those listed in Table III.

                                      TABLE III                                    __________________________________________________________________________     L or D Amino Acid Residue                                                       ##STR17##                                                                                                SUBSTITUENTS OF                                     NATURAL SUBSTITUENTS       HOMOLOGUES & ANALOGUES.sup.1                        NAME R.sub.a        R.sub.b                                                                           R.sub.c                                                                            R.sub.a           R.sub.b                                                                           R.sub.c                        __________________________________________________________________________     Gly  H              H  H   H                 U  U.sub.1                        Ala  CH.sub.3       H  H   CH.sub.3          U  U.sub.1                                                   CH.sub.2          -- U.sub.                         Val  CH(CH.sub.3).sub.2                                                                            H  H   CH(CH.sub.3).sub.2                                                                               U  U.sub.1                                                   C(CH.sub.3).sub.3 U  U.sub.1                                                   C(CH.sub.3).sub.2 -- U.sub.                         Leu  CH.sub.2 CH(CH.sub.3).sub.2                                                                   H  H   (CH.sub.2).sub.n+1 CH(CH.sub.3).sub.2                                                            U  U.sub.1                                                   (CH.sub.2).sub.n+1 C(CH.sub.3).sub.3                                                             U  U.sub.1                                                   CHCH(CH.sub.3).sub.2                                                                             -- U.sub.                                                    CH(CH.sub.2).sub.n CH(CH.sub.3).sub.2                                                            -- U.sub.                         Ile                                                                                  ##STR18##     H  H                                                                                   ##STR19##        U  U.sub.1                        NIle CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.3                                                           H  H   CH.sub.2).sub.n+1 CH.sub.3                                                                       U  U.sub.1                                                   CH(CH.sub.2).sub.n CH.sub.3                                                                      -- U.sub.                         Pro                                                                                  ##STR20##     H                                                                                      ##STR21##        U                                                             ##STR22##        U                                                             ##STR23##        .sub. U.sub.1                                                 ##STR24##        U                                 Ser  CH.sub.2 OH    H  H   (CH.sub.2).sub.n+1 OU                                                                            .sub. U.sub.1                                                                     U.sub.2                        Thr  CHOHCH.sub.3   H  H   (CH.sub.2).sub.n+1 CHOUCH.sub.3                                                                  .sub. U.sub.1                                                                     U.sub.2                        Cys  CH.sub.2 SH    H  H   (CH.sub.2).sub.n+1 SU                                                                            .sub. U.sub.1                                                                     U.sub.2                                                   (CH.sub.2).sub.n+1 SO.sub.3 H                                                                    U  U.sub.1                        Met  CH.sub.2 CH.sub.2 SCH.sub.3                                                                   H  H   (CH.sub.2).sub.n+1 SCH.sub.3                                                                     U  U.sub.1                                                   CH(CH.sub.2).sub.n+1 SCH.sub.3                                                                   -- U.sub.1                                                   (CH.sub.2).sub.n+1 SOCH.sub.3                                                                    U  U.sub.1                                                   CH(CH.sub.2).sub.n+1 SOCH.sub.3                                                                  -- U.sub.1                                                   (CH.sub.2).sub.n+1 SO.sub.2 CH.sub.3                                                             U  U.sub.1                                                   CH(CH.sub.2).sub.n+1 SO.sub.2 CH.sub.3                                                           -- U.sub.                         Asp   CH.sub.2 CO.sub.2 H                                                                          H  H   (CH.sub.2).sub.n+1 CO.sub.2 U                                                                    .sub. U.sub.1                                                                     U.sub.2                                                   CH(CH.sub.2).sub.n CO.sub.2 U                                                                    -- U.sub.1                        Glu  (CH.sub.2).sub.2 CO.sub.2 H                                                                   H  H   (CH.sub.2).sub.n+1 CO.sub.2 U                                                                    .sub. U.sub.1                                                                     U.sub.2                        Asn  CH.sub.2 CONH.sub.2                                                                           H  H   (CH.sub.2).sub.n+1 CONR.sub.1 R.sub.2                                                            U  U.sub.1                                                   CH(CH.sub.2).sub.n CONR.sub.1 R.sub.2                                                            -- U.sub.                         Gln  (CH.sub.2).sub.2 CONH.sub.2                                                                   H  H   (CH.sub.2).sub.n+1 CONR.sub.1 R.sub.2                                                            U  U.sub.1                        Arg                                                                                  ##STR25##     H  H                                                                                   ##STR26##        .sub. U.sub.1                                                                     U.sub.2                                                    ##STR27##        .sub. U.sub.1                                                                     U.sub.2                        Lys  (CH.sub.2).sub.4 NH.sub.2                                                                     H  H                                                                                   ##STR28##        U  U.sub.3                                                    ##STR29##        U  U.sub.4                        His                                                                                  ##STR30##     H  H                                                                                   ##STR31##        U  U.sub.1                                                    ##STR32##        U  U.sub.1                                                    ##STR33##        U  U.sub.1                                                    ##STR34##        U  U.sub.1                                                    ##STR35##        U  U.sub.1                                                    ##STR36##        U  U.sub.1                                                    ##STR37##        U  U.sub.1                                                    ##STR38##        U  U.sub.1                                                    ##STR39##        U  U.sub.1                                                    ##STR40##        U  U.sub.1                                                    ##STR41##        U  U.sub.1                                                    ##STR42##        U  U.sub.1                                                    ##STR43##        U                                                             ##STR44##        U                                 Phe                                                                                  ##STR45##     H  H                                                                                   ##STR46##        U  U.sub.1                                                    ##STR47##        -- U.sub.1                                                    ##STR48##           U.sub.1                        Tyr                                                                                  ##STR49##     H  H   See Phe above                                       α-Naphth                                                                       ##STR50##     H  H                                                                                   ##STR51##        U  U.sub.1                                                    ##STR52##        -- U.sub.                         β-Naphth                                                                        ##STR53##     H  H                                                                                   ##STR54##        U  U.sub.1                                                    ##STR55##        -- U.sub.                         Trp                                                                                  ##STR56##     H  H                                                                                   ##STR57##        U  U.sub.1                        Sar  H              H  CH.sub.3                                                                           U                 .sub.  U.sub.1                                                                    CH.sub.3                       Iql                                                                                  ##STR58##     H  H                                                                                   ##STR59##        U  U.sub.1                        __________________________________________________________________________      .sup.1 LEGEND:                                                                 U, U.sub.1, U.sub.2, U.sub.3 and U.sub.4 are selected from a group             consisting of hydrogen, alkyl groups having from 1-10 carbon atoms, and        benzyl.                                                                        B, B.sub.1, and B.sub.2 are selected from a group consisting of ND, O, S.      D, D.sub.1, D.sub.2, and D.sub.3 are selected from a group consisting of       hydrogen, methyl, ethyl, propyl, benzyl, formyl, and tosyl.                    K.sub.1, K.sub.2, K.sub.3, K.sub.4, K.sub.5, K.sub.6, and K.sub.7 are N o      CG, provided that adjacent positions are not both N.                           G is selected from a group consisting of hydrogen, halogen, OU, OR.sub.x,      SR.sub.x, R.sub.x, SO.sub.3 R.sub.x, B(OH).sub.2, NR.sub.x SOR.sub.y,          NR.sub.x R.sub.y, CN, N(R.sub.x)COR.sub.y, SOR.sub.x, SO.sub.2 R.sub.x,        SO.sub.2, CO.sub.2 R.sub.x, CONR.sub.x R.sub.y, CONR.sub.x COR.sub.y,          wherein R.sub.x and R.sub.y are selected from a group consisting of            hydrogen and straight and branched alkyl groups containing 1-6 carbon          atoms, and substituted straight and branched alkyl groups containing 1-6       carbon atoms, wherein the substituents include, but are not limited to,        one or more halo, hydroxy, amino, and mercapto groups.                         L is N or N.sup.+D.                                                            R.sub.1 and R.sub.2 are as defined in Table I.                                 n is an integer from 0 to 4.                                             

The term "pharmaceutically acceptable salts", as used herein, refers to the non-toxic alkali metal, alkaline earth metal and ammonium salts commonly used in the pharmaceutical industry including, but not limited to, the sodium, potassium, lithium, calcium, magnesium, barium, ammonium and protamine salts which are prepared by methods well known in the art. The term also includes non-toxic acid addition salts which are generally prepared by reacting the compounds of this invention with a suitable organic or inorganic acid. Representative salts include, but are not limited to, the hydrochloride, hydrobromide, sulfate, bisulfate, acetate, oxalate, valerate, oleate, laurate, borate, benzoate, lactate, phosphate, tosylate, citrate, maleate, fumarate, succinate, tartrate, napsylate, and the like.

Preferably, the peptides of this invention have the amino acid sequence represented by formula I, supra, wherein a is 0 or 1, b is 0 and X₁ and X₂ are selected from a group consisting of --R, --OR, and RC(O)--, wherein R is selected from a group consisting of hydrogen and straight and branched chain alkyl groups containing 1-6 carbon atoms; A₁ and A₄ are selected from the group consisting of histidyl, tryptophyl, phenylalanyl, tyrosyl, homologues and analogues thereof, and, with respect to A₁, the desamino forms thereof; A₂ and A₅ are selected from the group consisting of D-histidyl, D-tryptophyl, D-phenylalanyl, D-tyrosyl, homologues and analogues thereof; A₃ is selected from the group consisting of glycyl, alanyl, seryl, asparaginyl, prolyl, D-alanyl, D-seryl, D-asparaginyl, D-prolyl, and homologues and analogues thereof; A₆ is selected from the group consisting of arginine, lysine, ornithine, histidine, aspartic acid, glutamic acid, asparagine, glutamine, D-arginine, D-lysine, D-ornithine, D-histidine, D-aspartic acid, D-glutamic acid, D-asparagine, D-glutamine, D-arginine, homologues and analogues thereof, and the descarboxy forms thereof; Y is selected from a group consisting of --CH₂ OH, --OR, and --NR₁ R₂, wherein R, R₁, and R₂ are selected from a group consisting of hydrogen and straight and branched chain alkyl groups containing 1-6 carbon atoms; and the pharmaceutically acceptable salts thereof.

More preferably, the peptides of this invention have the amino acid sequence represented by formula II: ##STR60## wherein a is 0 or 1; X₂ is selected from the group consisting of R-- and RC(O)--; wherein R is selected from the group consisting of hydrogen and alkyl groups containing 1-2 carbon atoms; A₁ is selected from the group consisting of tyrosyl, O-methyltyrosyl, histidyl, 3-N-methylhistidyl, p-chlorophenylalanyl, and the desamino forms thereof; A₃ is selected from the group consisting of alanyl, seryl, and D-alanyl; A₄ is selected from the group consisting of tryptophyl and tyrosyl; A₅ is selected from the group consisting of D-phenylalanyl, D-histidyl, D-tyrosyl, and D-p-chlorophenylalanyl; A₆ is selected from the group consisting of arginine, homoarginine, lysine, ornithine, aspartic acid, glutamic acid, asparagine, glutamine, and D-lysine; and Y is selected from the group consisting of --OR and --NHR, wherein R is selected from the group consisting of hydrogen and alkyl groups containing 1-2 carbon atoms; and the pharmaceutically acceptable salts thereof.

Peptides within the scope of the instant invention include, but are not limited to, those set forth in Table IV and the desamino and/or descarboxy forms thereof, wherein the respective positions of X₁, X₂, X₃ are set forth in formula I.

                  TABLE IV                                                         ______________________________________                                         (X.sub.1 -,(X.sub.2 -).sub.a,(X.sub.3 -).sub.b)-His-D-Trp-Ala-Trp-D-Phe-Ly     s-Y                                                                            (X.sub.1 -,(X.sub.2 -).sub.a,(X.sub.3 -).sub.b)-His-D-5-Br-Trp-Ala-Trp-D-P     he-Lys-Y                                                                       (X.sub.1 -,(X.sub.2 -).sub.a,(X.sub.3 -).sub.b)-His-D-Trp-Ala-5-Br-Trp-D-P     he-Lys-Y                                                                       (X.sub.1 -,(X.sub.2 -).sub.a,(X.sub.3 -).sub.b)-1-N-Me-His-D-Trp-Ala-Trp-D     -Phe-Lys-Y                                                                     (X.sub.1 -,(X.sub.2 -).sub.a,(X.sub.3 -).sub.b)-3-N-Me-His-D-Trp-Ala-Trp-D     -Phe-Lys-Y                                                                     (X.sub.1 -,(X.sub.2 -).sub.a,(X.sub.3 -).sub.b)-Arg-D-Trp-Ala-Iql-D-Phe-Ar     g-Y                                                                            (X.sub.1 -,(X.sub.2 -).sub.a,(X.sub.3 -).sub.b)-Lys-D-Trp-Ala-Trp-D-Phe-Gl     u-Y                                                                            (X.sub.1 -,(X.sub.2 -).sub.a,(X.sub.3 -).sub.b)-His-D-Trp-Ser-Trp-D-Phe-Ly     s-Y                                                                            (X.sub.1 -,(X.sub.2 -).sub.a,(X.sub.3 -).sub.b)-Tyr-D-Trp-D-Ala-Trp-D-His-     Gln-Y                                                                          (X.sub.1 -,(X.sub.2 -).sub.a,(X.sub.3 -).sub.b)-Tyr-D-Trp-Ala-Trp-D-1-N-Me     -His-Met-Y                                                                     (X.sub.1 -,(X.sub.2 -).sub.a,(X.sub.3 -).sub.b)-Tyr-D-Trp-Ala-Trp-D-3-N-Me     -His-Pro-Y                                                                     (X.sub.1 -,(X.sub.2 -).sub.a,(X.sub.3 -).sub.b)-Tyr-D-Trp-Ala-Trp-D-Arg-Hi     s-Y                                                                            (X.sub.1 -,(X.sub.2 -).sub.a,(X.sub.3 -).sub.b)-Tyr-D-Trp-Ala-Trp-D-Lys-Se     r-Y                                                                            (X.sub.1 -,(X.sub.2 -).sub.a,(X.sub.3 -).sub.b)-Tyr-D-Trp-D-Ser-Trp-D-Lys-     Phe-Y                                                                          (X.sub.1 -,(X.sub.2 -).sub.a,(X.sub.3 -).sub.b)-His-D-Trp-Ala-Trp-D-His-Tr     p-Y                                                                            (X.sub.1 -,(X.sub.2 -).sub.a,(X.sub.3 -).sub.b)-Arg-D-Phe-Val-Tyr-D-Lys-D-     Lys-Y                                                                          (X.sub.1 -,(X.sub.2 -).sub.a,(X.sub.3 -).sub.b)-Tyr-D-Tyr-Met-Phe-D-Arg-D-     Orn-Y                                                                          (X.sub.1 -,(X.sub.2 -).sub.a,(X.sub.3 -).sub. b)-Phe-D-Phe-Gln-Phe-D-1-N-M     e-His-D-Asp-Y                                                                  (X.sub.1 -,(X.sub.2 -).sub.a,(X.sub.3 -).sub.b)-His-D-Trp-Ile-Tyr-D-Trp-D-     Glu-Y                                                                          (X.sub.1 -,(X.sub.2 -).sub.a,(X.sub.3 -).sub.b)-α-Naphth-D-Trp-D-Ala     -β-Naphth-D-Phe-Val-Y                                                     (X.sub.1 -,(X.sub.2 -).sub.a,(X.sub.3 -).sub.b)-β-Naphth-D-Lys-D-His-     His-D-Arg-Thr-Y                                                                ______________________________________                                    

The peptides of the instant invention can be prepared by solution methods known in the art or by using standard solid-phase techniques. The solid-phase synthesis, for example, can be commenced from the C-terminal end of the peptide using an α-amino protected amino acid. A suitable starting material can be prepared, for instance, by attaching the required α-amino acid to a chloromethyl resin, a hydroxymethyl resin, a benzhydrylamine (BHA) resin, or a p-methylbenzylhydrylamine (p-Me-BHA) resin. One such chloromethyl resin is sold under the tradename BIO-READS SX-1 by Bio Rad Laboratories, Richmond, Calif. The preparation of the hydroxymethyl resin is described by Bodansky et al., Chem. Ind. (London) 38, 1597 (1966). The BHA resin has been described by Pietta and Marshall, Chem. Commn. 650 (1970) and is commercially available from Beckman Instruments, Inc., Palo Alto, Calif. in the hydrochloride form thereof (BHA.HCl).

In the solid-phase preparation of the compounds of this invention, a protected amino acid can be coupled to a resin with the aid of a coupling agent. After the initial coupling, the α-amino protecting group can be removed by a choice of reagents including trifluoroacetic acid (TFA) or hydrochloric acid (HCl) solutions in organic solvents at room temperature. After removal of the α-amino protecting group, the remaining protected amino acids can be coupled stepwise in the desired order. Each protected amino acid can be generally reacted in about a 3-fold excess using an appropriate carboxyl group activator such as dicyclohexylcarbodiimide (DCC) in solution, for example, in methylene chloride(CH₂ Cl₂)-dimethylformamide (DMF) mixtures.

After the desired amino acid sequence has been completed, the desired peptide can be cleaved from the resin support by treatment with a reagent such as hydrogen fluoride (HF) which not only cleaves the peptide from the resin, but also cleaves all remaining side-chain protecting groups. When a chloromethyl resin or hydroxymethyl resin is used, HF treatment results in the formation of the free peptide acids of Formula I (Y=--COOH). When the BHA or p-Me-BHA resin is used, HF treatment results directly in the free peptide amides of Formula I (Y=--CONH₂). Alternatively, when the chloromethylated or hydroxymethyl resin is employed, the side-chain protected peptide can be cleaved from the resin by treatment of the peptide-resin with ammonia to give the desired side-chain protected amide or with an alkylamine to give a side-chain protected alkylamide or dialkylamide. Side-chain protection can then be removed in the usual fashion by treatment with HF to give the free peptide amides, alkylamides, or dialkylamides.

In preparing the esters of this invention, the resins used to prepare the acids of Formula I (Y=--COOH) can be employed and the side-chain protected peptide can be cleaved with a base and an appropriate alcohol, i.e., methanol. Side-chain protecting groups can then be removed in the usual fashion by treatment with HF to obtain the desired ester.

The solid-phase procedure discussed above is well known in the art and has been essentially described by Stewart and Young, Solid Phase Peptide Synthesis, Freeman and Co., San Francisco (1969).

Some of the well known solution methods which can be employed to synthesize the peptides of the instant invention are set forth in Bodansky et al., Peptide Synthesis, 2nd Edition, John Wiley & Sons, New York, N.Y. 1976).

Accordingly, also within the scope of the instant invention are intermediate compositions prepared during the synthesis of the novel peptides of formula I. Intermediate compositions prepared via solid-phase techniques are the peptide-resin compounds of formula III and intermediate compositions prepared via solution techniques are the protected peptide-compounds of formulas IV-VI: ##STR61##

    B.sub.1 -B.sub.2 -B.sub.3 -B.sub.4 -B.sub.5 -B'.sub.6 -Y   (VI)

wherein Pr₁ is an α-amino protecting group; q, r, and s are each either 0 or 1; a and b are as defined above; m is either 0 or 1; X'₁, X'₂, and X'₃ are selected from a group consisting of N-terminal and desamino alpha-carbon substitutions and radicals; B₁ and B₄ are selected from a group consisting of histidyl, arginyl, lysyl, α-naphthylalanyl, β-naphthylalanyl, isoquinolyl, tyrosyl, tryptophyl, phenylalanyl, homologues and analogues thereof, the side-chain protected forms thereof, and, with respect to B₁, the desamino forms thereof; B₂, B₅, and B'₅ are selected from a group consisting of D-histidyl, D-arginyl, D-lysyl, D-α-naphthylalanyl, D-β-naphthylalanyl, D-isoquinolyl, D-tyrosyl, D-tryptophyl, D-phenylalanyl, homologues and analogues thereof, the side-chain protected forms thereof, and, with respect to B'₅, the descarboxy forms thereof; B₃ is selected from a group consisting of glycyl, alanyl, valyl, leucyl, isoleucyl, prolyl, seryl, threonyl, methionyl, aspartyl, glutamyl, asparginyl, glutaminyl, histidyl, D-alanyl, D-valyl, D-leucyl, D-isoleucyl, D-prolyl, D-seryl, D-threonyl, D-methionyl, D-aspartyl, D-glutamyl, D-asparaginyl, D-glutaminyl, D-histidyl, homologues and analogues thereof, and the side-chain protected forms thereof; B₆ and B'₆ are selected from a group consisting of amino acids of the L- and D-configuration, homologues and analogoues thereof, the side-chain protection forms thereof, and, with respect to B'₆, the descarboxy forms thereof; ® is a resin; Y is as defined above; and Pr₂ is a carboxyl protecting group.

Preferably, the peptide-resins of this invention are represented by formula III, and the protected peptide-compounds are represented by formulas IV-VI, supra, wherein B₁ and B₄ are selected from the group consisting of histidyl, tryptophyl, phenylalanyl, tyrosyl, homologues and analogues thereof, the side-chain protected forms thereof, and, with respect to B₁, the desamino forms thereof; B₂ and B₅ are selected from the group consisting of D-histidyl, D-tryptophyl, D-phenylalanyl, D-tyrosyl, homologues and analogues thereof, and the side-chain protected forms thereof; B₃ is selected from the group consisting of glycyl, alanyl, seryl, asparaginyl, prolyl, D-alanyl, D-seryl, D-asparaginyl, D-prolyl, homologues and analogues thereof, and the side-chain protected forms thereof, and B₆ and B'₆ are selected from the group consisting of arginine, lysine, ornithine, histidine, aspartic acid, glutamic acid, asparagine, glutamine, D-arginine, D-lysine, D-ornithine, D-histidine, D-aspartic acid, D-glutamic acid, D-asparagine, D-glutamine, D-arginine, homologues and analogues thereof, and the descarboxy forms thereof; and, with respect to B'₆, the descarboxy forms thereof, and the side-chain protection forms thereof.

More preferably, the peptide-resins of this invention are represented by formula VII and the protected peptide-compounds are represented by formulas VIII-X: ##STR62##

    B.sub.1 -D-Trp-B.sub.3 -B.sub.4 -B.sub.5 -B'.sub.6 -Y      (X)

wherein B₁ is selected from the group consisting of tyrosyl, O-methyltyrosyl, histidyl, 3-N-methylhistidyl, p-chlorophenylalanyl, the desamino forms thereof, and the side-chain protected forms thereof; B₃ is selected from the group consisting of alanyl, seryl, D-alanyl and the side-chain protected forms thereof; B₄ is selected from the group consisting of tryptophyl, tyrosyl and the side-chain protected forms thereof; B₅ is selected from the group consisting of D-phenylalanyl, D-histidyl, D-tyrosyl, D-p-chlorophenylalanyl, and the side-chain protected forms thereof; and B₆ and B'₆ are selected from the group consisting of arginine, homoarginine, lysine, ornithine, aspartic acid, glutamic acid, asparagine, glutamine, and D-lysine.

Suitable α-amino acid protecting groups Pr₁, include, but are not limited to, tertiary-butyloxycarbonyl (BOC), isoamyloxycarbonyl (AOC), o-nitrophenylsulfenyl (NPS), fluorenylmethyloxycarbonyl (FMOC), o-nitropyridinylsulfenyl (NPYS), and biphenylproploxycarbonyl (BPOC).

Suitable carboxyl protecting groups, Pr₂, include, but are not limited to, salts (e.g., Li⁺, Na⁺ CS⁺, etc.), methyl, ethyl, benzyl, benzhydryl, substituted benzyl, phthalimidomethyl, tertiary butyl, phenacyl, phenyl, 4-picolyl, 2-methylthioethyl, 2(p-toluenesulfonyl)ethyl, 2-(p-nitrothiophenyl)ethyl, p-methylthiophenyl, and hydrazides.

In addition to the resins, ®, noted above, other resins include, but are not limited to, phenylacetamidomethyl (PAM), chloromethyl, and poly-N-acrylpyrrolidine resins.

                                      TABLE V                                      __________________________________________________________________________     NTerminus and Desamino Substitutions and Radicals.sup.1                        X'.sub.1      X'.sub.2                                                                               X'.sub.3                                                                               a b m q r s                                      __________________________________________________________________________     NTerminus Substitutions and Radicals                                           R.sub.1(R.sub.1 ≠ H)                                                                   R.sub.2(R.sub.2 ≠ H)                                                             --      1 0 1 0 0 0                                      --            R.sub.2 --      1 0 0 1 0 0                                      R.sub.1(R.sub.1 ≠ H)                                                                   R.sub.2(R.sub.2 ≠ H)                                                             R.sub.3(R.sub.3 ≠ H)                                                             1 1   0 0 0                                      R.sub.1       R.sub.2 R.sub.3 1 1 1 0 0 0                                       ##STR63##    R.sub.2 --      1 0 1 0 0 0                                       ##STR64##    R.sub.2 --      1 0 1 0 0 0                                      R.sub.1       O       --      1 0 1 0 1 0                                       ##STR65##    R.sub.3(R.sub.3 ≠ H)                                                             --      1 0 1 0 0 0                                       ##STR66##    --      --      0 0 1 0 1 0                                       ##STR67##    --      --      0 0 1 1 1 0                                       ##STR68##    R.sub.3(R.sub.3 ≠ H)                                                             --      1 0 1 1 0 0                                       ##STR69##    R.sub.3(R.sub.3 ≠ H)                                                             --      1 0 1 0 0 0                                       ##STR70##    --      --      0 0 1 0 1 0                                       ##STR71##    R.sub.3(R.sub.3 ≠ H)                                                             --      1 0 1 1 0 0                                      Desamino Substituents and Radicals                                             R             --      --      0 0 1 0 0 0                                      RZ(R ≠ H)                                                                              --      --      0 0 1 0 0 0                                      Z             --      --      0 0 1 1 0 0                                      __________________________________________________________________________      .sup.1 LEGEND: R, R.sub.1, R.sub.2, R.sub.3, and Z are as defined in TABL      1, supra.                                                                

Virtually any suitable N-terminal and desamino alpha-carbon substitution and radical can be used in the instant invention. Typical N-terminal and desamino alpha-carbon substitutions and radicals include, but are not limited to, those set forth in Table V.

The growth hormone releasing peptides of Formula I are useful in vitro as unique tools for understanding how growth hormone secretion is regulated at the pituitary level. This includes use in the evaluation of many factors thought or known to influence growth hormone secretion such as age, sex, nutritional factors, glucose, amino acids, fatty acids, as well as fasting and non-fasting states. In addition, the peptides of this invention can be used in the evaluation of how other hormones modify growth hormone releasing activity. For example, it has already been established that somatostatin inhibits growth hormone release. Other hormones that are important and in need of study as to their effect on growth hormone release include the gonadal hormones, e.g., testosterone, estradiol, and progesterone; the adrenal hormones, e.g., cortisol and other corticoids, epinephrine and norepinephrine; the pancreatic and gastrointestinal hormones, e.g., insulin, glucagon, gastrin, secretin; the vasoactive intestinal peptides, e.g., bombesin; and the thyroid hormones, e.g., thyroxine and triiodothyronine. The peptides of Formula I can also be employed to investigate the possible negative or positive feedback effects of some of the pituitary hormones, e.g., growth hormone and endorphin peptides, on the pituitary to modify growth hormone release. Of particular scientific importance is the use of these peptides to elucidate the subcellular mechanisms mediating the release of growth hormone.

The peptides of Formula I can also be administered to animals, including man, to release growth hormone in vivo. For example, the peptides can be administered to commercially important animals such as swine, cattle, sheep and the like to accelerate and increase their rate and extent of growth, and to increase milk production in such animals. In addition, these peptides can be administered to humans in vivo as a diagnostic tool to directly determine whether the pituitary is capable of releasing growth hormone. For example, the peptides of formula I can be administered in vivo to children. Serum samples taken before and after such administration can be assayed for growth hormone. Comparison of the amounts of growth hormone in each of these samples would be a means for directly determining the ability of the patient's pituitary to release growth hormone.

Accordingly, the present invention includes within its scope pharmaceutical compositions comprising, as an active ingredient, at least one of the peptides of Formula I in association with a pharmaceutical carrier or diluent. Optionally, the active ingredient of the pharmaceutical compositions can comprise a growth promoting agent in addition to at least one of the peptides of Formula I or another composition which exhibits a different activity, e.g., an antibiotic or other pharmaceutically active material.

Growth promoting agents include, but are not limited to, TRH, diethylstilbesterol, theophylline, enkephalins, E series prostaglandins, compounds disclosed in U.S. Pat. No. 3,239,345, e.g., zeranol, and compounds disclosed in U.S. Pat. No. 4,036,979, e.g., sulbenox.

The peptides of this invention can be administered by oral, parenteral (e.g., intramuscular, intraperitoneal, intravenous or subcutaneous injection, or implant), nasal, vaginal, rectal, sublingual, or topical routes of administration and can be formulated in dosage forms appropriate for each route of administration.

Solid dosage forms for oral administration include capsules, tablets, pills, powders and granules. In such solid dosage forms, the active compound is admixed with at least one inert pharmaceutically acceptable carrier such as sucrose, lactose, or starch. Such dosage forms can also comprise, as is normal practice, additional substances other than inert diluents, e.g., lubricating agents such as magnesium stearate. In the case of capsules, tablets and pills, the dosage forms may also comprise buffering agents. Tablets and pills can additionally be prepared with enteric coatings.

Liquid dosage forms for oral administration include pharmaceutically acceptable emulsions, solutions, suspensions, syrups, the elixirs containing inert diluents commonly used in the art, such as water. Besides such inert diluents, compositions can also include adjuvants, such as wetting agents, emulsifying and suspending agents, and sweetening, flavoring, and perfuming agents.

Preparations according to this invention for parenteral administration include sterile aqueous or non-aqueous solutions, suspensions, or emulsions. Examples of non-aqueous solvents or vehicles are propylene glycol, polyethylene glycol, vegetable oils, such as olive oil and corn oil, gelatin, and injectable organic esters such as ethyl oleate. Such dosage forms may also contain adjuvants such as preserving, wetting, emulsifying, and dispersing agents. They may be sterilized by, for example, filtration through a bacteria-retaining filter, by incorporating sterilizing agents into the compositions, by irradiating the compositions, or by heating the compositions. They can also be manufactured in the form of sterile solid compositions which can be dissolved in sterile water, or some other sterile injectable medium immediately before use.

Compositions for rectal or vaginal administration are preferably suppositories which may contain, in addition to the active substance, excipients such as cocoa butter or a suppository wax.

Compositions for nasal or sublingual administration are also prepared with standard excipients well known in the art.

The dosage of active ingredient in the compositions of this invention may be varied; however, it is necessary that the amount of the active ingredient be such that a suitable dosage form is obtained. The selected dosage depends upon the desired therapeutic effect, on the route of administration, and on the duration of the treatment. Generally, dosage levels of between 0.001 to 10 mg/kg. of body weight daily are administered to animals, e.g., mammals, to obtain effective release of growth hormone.

The following examples are provided for the purpose of further illustration only and are not intended to be limitations on the disclosed invention.

EXAMPLE 1 Synthesis of H₂ -Tyr-D-Trp-Ala-Trp-D-Phe-Met-NH₂

BHA.HCl resin was placed in a reaction vessel. The following procedure was then employed in conjunction with a Beckman brand Peptide Synthesizer Model No. 990 in preparing the hexapeptide H₂ -Tyr-D-Trp-Ala-Trp-D-Phe-Met-NH₂ :

1. Methylene chloride (CH₂ Cl₂ ; about 10 ml/gm of BHA.HCl resin) was added to the reaction vessel. The BHA.HCl resin was washed with vigorous stirring for about 1.5 minutes. The CH₂ Cl₂ solution was then drained from the reaction vessel. This washing step was repeated once.

2. A triethylamine solution ((Et₃ N)/CH₂ Cl₂ (10:90); about 10 ml/gm BHA.HCl resin) was added to the washed BHA.HCl resin in the reaction vessel. The resulting mixture was vigorously stirred for about 1.5 minutes. The solution was then drained from the reaction vessel.

3. Another Et₃ N/CH₂ Cl₂ (10:90) solution (about 10 ml/gm BHA.HCl) was added to the reaction vessel. The BHA.HCl resin was neutralized by vigorous stirring for about 20 minutes. The solution was then drained from the reaction vessel.

4. CH₂ Cl₂ (about 10 ml/gm of BHA.HCl resin) was added to the reaction vessel. The resulting mixture was vigorously stirred for about 1.5 minutes. The solution was then drained from the reaction vessel. This procedure was repeated an additional two times.

5. Tertiarybutyloxycarbonyl-methionine (Boc-Met; about 2.5 times the theoretical amount of the total binding capacity of the BHA.HCl resin originally placed in the reaction vessel) in about 50 ml of dimethylformamide-methylene chloride solution (DMF--CH₂ Cl₂ (1:9)) was added to the reaction vessel. The resulting mixture was vigorously stirred for about 1.5 minutes.

6. A 0.5 molar (M) dicyclohexylcarbodiimide (DCC) in CH₂ Cl₂ solution (about 2.5 times the theroretical amount of total binding capacity of the BHA.HCl resin originally placed in the reaction vessel) was added to the reaction vessel. The resulting mixture was vigorously stirred until a negative ninhydrin test was obtained (about 120 minutes). The solution was then drained from the reaction vessel.

7. CH₂ Cl₂ (about 10 ml/gm of BHA.HCl resin) was added to the reaction vessel. The resulting solution was vigorously stirred for about 1.5 minutes. The solution was then drained from the reaction vessel. This washing procedure was repeated once.

8. DMF (about 10 ml/gm of BHA.HCl resin) was added to the reaction vessel. The resulting mixture was stirred for about 1.5 miutes. The solution was then drained from the reaction vessel.

9. CH₂ Cl₂ (about 10 ml/gm of BHA.HCl resin) was added to the reaction vessel. The resulting mixture was vigorously stirred for about 1.5 minutes. The solution was then drained from the reaction vessel. This washing procedure was repeated an additional two times.

10. A trifluoroacetic acid/methylene chloride solution (TFA/CH₂ Cl₂ (40:60); about 10 ml/gm of BHA.HCl resin) was added to the reaction vessel. The resulting mixture was vigorously stirred for about 1.5 minutes. The solution was then drained from the reaction vessel.

11. Another TFA/CH₂ Cl₂ (40:60) solution (about 10 ml/gm of BHA.HCl resin) was added to the reaction vessel. The resulting mixture was vigorously stirred for about 20 minutes. The solution was then drained from the reaction vessel.

12. CH₂ Cl₂ (about 10 ml/gm of BHA.HCl resin) was added to the reaction vessel. The resulting solution was vigorously stirred for about 1.5 minutes. The solution was then drained from the reaction vessel. This washing procedure was repeated once.

13. A triethylamine solution ((Et₃ N)/CH₂ Cl₂ (10:90); about 10 ml/gm BHA.HCl resin) was added to the washed BHA.HCl resin in the reaction vessel. The resulting mixture was vigorously stirred for about 1.5 minutes. The solution was then drained from the reaction vessel.

14. Another Et₃ N/CH₂ Cl₂ (10:90) solution (about 10 ml/gm BHA.HCl) was added to the reaction vessel. The BHA.HCl resin was neutralized by vigorous stirring for about 20 minutes. The solution was then drained from the reaction vessel.

15. Chloroform (CHCl₃ ; about 10 ml/gm of BHA.HCl resin) was added to the reaction vessel. The resulting mixture was vigorously stirred for about 1.5 minutes. The solution was then drained from the reaction vessel.

16. An ethanol/methylene chloride solution (EtOH/CH₂ Cl₂ (30:70); about 10 ml/gm of BHA.HCl resin) was added to the reaction vessel. The resulting mixture was vigorously stirred for about 1.5 minutes. The solution was then drained from the reaction vessel. This washing step was repeated once.

Steps 4 through 16 were then repeated employing the following sequence of amino acids:

Boc-D-Phe

Boc-Trp

Boc-Ala

Boc-D-Trp

Boc-Tyr (BrZ*)

After completion of the synthesis of the desired peptide resin, the reaction vessel containing the peptide resin was then placed in a dessicator and dried overnight under a vacuum. The dried peptide resin was removed from the reaction vessel and placed in another vessel suitable for HF cleavage. This latter vessel also contained a magnetic stirring bar. A quantity of anisole sufficient to wet the peptide resin was added to this vessel. The vessel was next connected to an HF line and placed under a vacuum to remove any air therein. The vessel was then cooled to about -78° C. with a dry ice-acetone bath. Doubly distilled HF (about 10 ml/gm of peptide resin) was added to the vessel. The dry ice-acetone bath was then removed from the vessel and replaced by an ice-water bath. The vessel's contents were vigorously stirred for about 45 minutes while the vessel remained immersed in the ice-water bath. Most of the HF in the vessel was then removed by water aspiration. After the majority of HF was removed by water aspiration, the remaining HF and anisole were removed via a vacuum pump.

The vessel's contents were washed with about 100 ml of ether to further remove any residual anisole.

The peptide was removed from the resin by extraction with 30% aqueous acetic acid (aq.HOAc). The aq.HOAc was lyophilized off to yield a fluffy peptide powder.

The peptide was then purified by partition chromatography or counter current distribution (CCD) employing a butanol:HOAc:water (4:1:5) system. When further purification was necessary, a Pharmacia LH-20 brand chromatography column was also employed.

EXAMPLE 2 Synthesis of H₂ -Tyr-D-Trp-Ala-Trp-D-Phe-Thr-NH₂

The procedure set forth in Example 1 was employed to synthesize the hexapeptide H₂ -Tyr-D-Trp-Ala-Trp-D-Phe-Thr-NH₂ employing the following sequence of amino acids:

Boc-Thr(Bzl*)

Boc-D-Phe

Boc-Trp

Boc-Ala

Boc-D-Trp

Boc-Tyr(BrZ)

EXAMPLE 3 Synthesis of H₂ -Tyr-D-Trp-Ala-Trp-D-Phe-Gln-OH

The procedure set forth in Example 1 was employed to synthesize the hexapeptide H₂ -Tyr-D-Trp-Ala-Trp-D-Phe-Gln-OH employing the following sequence of amino acids:

Boc-Glu-α-benzyl ester

Boc-D-Phe

Boc-Trp

Boc-Ala

Boc-D-Trp

Boc-Tyr(BrZ)

EXAMPLE 4 Synthesis of H₂ -Tyr-D-Trp-Ala-Trp-D-Phe-Gln-NH₂

The procedure set forth in Example 1 was employed with several modifications to synthesize the hexapeptide H₂ -Tyr-D-Trp-Ala-Trp-D-Phe-Gln-NH₂. The modifications consisted of:

(1) Omitting steps 2-4 of Example 1 and replacing them with a single step which entailed dissolving Boc-Gln (about 5 times the theoretical amount of the total binding of the BHA.HCl resin originally placed in the reaction vessel) in 10 ml of a CH₃ Cl₂ -DMF solution (3:2) present in a round bottom flask. The flask and its contents was cooled in ice and then DCC (about 1.25 times the theoretical amount of the total binding capacity of the BHA.HCl resin originally placed in the reaction vessel) was added to the flask. The resulting mixture was stirred in an ice bath for about 25-30 minutes. The DCC urea precipitate formed by the reaction between Boc-Gln and DCC was separated from the supernatant via filtration. The supernature comprising the CH₂ Cl₂ -DMF solution having a symmetrical anhydride (also formed by the reaction between Boc-Gln and DCC) dissolved therein was added to the reaction vessel. The resulting mixture was stirred until a negative ninhydrin test was obtained. The solution was then drained from the reaction vessel.

(2) After completing steps 7 through 16 of Example 1, steps 4 through 16 of Example 1 were then repeated, without modification, employing the following sequence of amino acids:

Boc-D-Phe

Boc-Trp

Boc-Ala

Boc-D-Trp

Boc-Try(BrZ)

EXAMPLE 5 Synthesis of H₂ -Tyr-D-Trp-Ala-Trp-D-Phe-Asn-NH₂

The procedure set forth in Example 1 was employed with several modifications to synthesize the hexapeptide H₂ -Tyr-D-Trp-Ala-Trp-D-Phe-Asn-NH₂. The modifications consisted of:

(1) Omitting steps 2-4 of Example 1 and replacing them with a simple step which entailed dissolving Boc-Asn (about 5 times the theoretical amount of the total binding capacity of the BHA.HCl resin originally placed in the reaction vessel) in about 50 ml of DMF in a suitable flask. The resulting solution was added to the reaction vessel to form a mixture. The mixture was vigorously stirred until a negative ninhydrin test was obtained. The solution was then drained from the reaction vessel.

(2) After completing steps 7 through 16 of Example 1, steps 4 through 16 of Example 1 were then repeated, without modification, employing the following sequence of amino acids:

Boc-D-Phe

Boc-Trp

Boc-Ala

Boc-D-Trp

Boc-Tyr(BrZ)

EXAMPLE 6 Synthesis of H₂ -His-D-Trp-D-Phe-Lys-NH₂

Para-methylbenzhydrylamine hydrochloride (p-Me-BHA.HCl) resin was placed in a reaction vessel. The following procedure, starting at step 6, was then employed in conjunction with a Beckman brand Peptide Synthesizer Model No. 990 in preparing the peptide H₂ -His-D-Trp-Ala-Trp-D-Phe-Lys-NH₂. The synthesis was started at step 6 because there was no amino acid present in the resin and one need only neutralize the resin which was initially in the HCl form.

1. Wash with methylene chloride (CH₂ Cl₂) for 1.5 minutes, three times.

2. Treat with trifluoroacetic acid-methylene chloride (40% TFA/CH₂ Cl₂, V/V) containing 0.1% indole for 1.5 minutes.

3. Repeat Step 2 for 20 minutes.

4. Wash with chloroform (CHCl₃) for 1.5 minutes, three times.

5. Wash with 30% ethanol-methylene chloride (30% EtOH/CH₂ Cl₂, V/V) for 1.5 minutes, two times.

6. Wash with CH₂ Cl₂ for 1.5 minutes, three times.

7. Treat with 10% triethylamine in CH₂ Cl₂ (10% TEA/CH₂ Cl₂, V/V) for 1.5 minutes.

8. Repeat Step 7 for 10 minutes.

9. Wash with CH₂ Cl₂ for 1.5 minutes, three times.

10. Add to the washed resin 2.5 equivalents of the appropriate protected amino acid in dimethyl formamide-methylene chloride (DMF-CH₂ Cl₂).

11. Add 0.5 N dicyclohexylcarbodiimide in CH₂ Cl₂ (DCC/CH₂ Cl₂); more than 2.5 equivalents.

12. Rinse addition funnel with CH₂ Cl₂ and add rinse to the reaction vessel.

13. Stir the reagents in Steps 10-12 for 2 hours or more.

14. Wash with CH₂ Cl₂ for 1.5 minutes, three times.

15. Wash with DMF for 1.5 minutes.

16. Wash with CH₂ Cl₂ for 1.5 minutes, two times.

17. Test by ninhydrin reaction according to the procedure of Kaiser et al., Annal. Biochem., 34:595 (1970).

18. If Step 17 shows complete reaction, repeat the above procedures starting from Step 1 employing the next protected amino acid. If Step 17 shows incomplete reaction, repeat Steps 7-17.

The above procedure was employed using the following sequence of amino acids:

Boc-Lys(ClZ⁺)

Boc-D-Phe

Boc-Trp

Boc-Ala

Boc-D-Trp

Boc-His(Tos*)

After completion of the synthesis of the desired peptide resin, the reaction vessel containing the peptide resin was then placed in a dessicator and dried overnight under a vacuum. The dried peptide resin was removed from the reaction vessel and placed in another vessel suitable for HF cleavage. This latter vessel also contained a magnetic stirring bar. A quantity of anisole sufficient to wet the peptide resin was added to this vessel. The vessel was next connected to an HF line and placed under a vacuum to remove any air therein. The vessel was then cooled to about -78° C. with a dry ice-acetone bath. Doubly distilled HF (about 10 ml/gm of peptide resin) was added to the vessel. The dry ice-acetone bath was then removed from the vessel and replaced by an ice-water bath. The vessel's contents were vigorously stirred for about 45 minutes while the vessel remained immersed in the ice-water bath. Most of the HF in the vessel was then removed by water aspiration. After the majority of HF was removed by water aspiration, the remaining HF and anisole were removed via a vacuum pump.

The vessel's contents were washed with about 100 ml of ether to further remove any residual anisole.

The peptide was removed from the resin by extraction with aqueous acetic acid (aq.HOAc). The aq.HOAc was lyophilized off to yield a fluffy peptide powder.

The peptide was then purified by partition chromatography or counter current distribution (CCD) employing a butanol:HOAc:water (4:1:5) system. When further purification was necessary, a Pharmacia LH-20 brand chromatography column was also employed.

EXAMPLE 7 Synthesis of H₂ -Tyr-D-Trp-Ala-Trp-D-Phe-Lys-NH₂

The procedue set forth in Example 6 can be employed to synthesize the peptide H₂ -Tyr-D-Trp-Ala-Trp-D-Phe-Lys-NH₂ employing the following sequence of amino acids:

Boc-Lys(ClZ)

Boc-D-His (Tos)

Boc-Trp

Boc-Ala

Boc-D-Trp

Boc-Tyr(BrZ*)

EXAMPLE 8 Synthesis of H₂ -Tyr-D-Trp-Ala-Trp-D-Phe-Glu-NH₂

The procedure set forth in Example 6 can be employed to synthesize the peptide H₂ -Tyr-D-Trp-Ala-Trp-D-Phe-Glu-NH₂ employing the following sequence of amino acids:

Boc-Glu-γ-Bzl*

Boc-D-Phe

Boc-Trp

Boc-Ala

Boc-D-Trp

Boc-Tyr(BrZ)

EXAMPLE 9 Synthesis of H₂ -Tyr-D-Trp-Ala-Trp-D-Phe-Phe-NH₂

The procedure set forth in Example 6 can be employed to synthesize the peptide H₂ -Tyr-D-Trp-Ala-Trp-D-Phe-Phe-NH₂ employing the following sequence of amino acids:

Boc-Phe

Boc-D-Phe

Boc-Trp

Boc-Ala

Boc-D-Trp

Boc-Tyr(BrZ)

EXAMPLE 10 Synthesis of H₂ -Tyr-D-Trp-Gly-Trp-D-Phe-Gln-NH₂

The procedure set forth in Example 6 can be employed with one modification to synthesize the peptide H₂ -Tyr-D-Trp-Gly-Trp-D-Phe-Gln-NH₂ employing the following sequence of amino acids:

Boc-Gln-ONP*

Boc-D-Phe

Boc-Trp

Boc-Gly

Boc-D-Trp

Boc-Tyr(BrZ)

The sole modification was made just in the procedure for coupling Boc-Gln-ONP to the resin. This modification consisted of the omission of step 11 of Example 6 in this one coupling procedure.

EXAMPLE 11 Synthesis of H₂ -His-D-Trp-D-Ala-Trp-D-Phe-Lys-OH

The procedure set forth in Example 6 can be employed with several modifications to synthesize the peptide H₂ -His-D-Trp-D-Ala-Trp-D-Phe-Lys-OH employing the following sequence of amino acids:

Boc-Lys(ClZ)

Boc-D-Phe

Boc-Trp

Boc-Ala

Boc-D-Trp

Boc-His(Tos)

The modifications were as follows:

1. A hydroxymethyl resin was employed instead of the p-Me-BHA.HCl resin.

2. Steps 6-18 were modified as follows just in the procedure for coupling Boc-Lys(ClZ) to the hydroxymethyl resin:

a. Step 6 was the same;

b. Steps 7 through 9 were omitted;

c. Steps 10 and 11 were the same;

d. Step 12 was omitted and the following procedure was substituted therefor:

Add 2.5 equivalents of N,N-dimethylaminopyridine (DMAP).

e. Steps 13 through 16 were the same;

f. Steps 17 and 18 were omitted and the following procedure was substituted therefor:

Dry the amino acid-resin under vacuum until a constant weight is obtained. If the final constant weight is equal to the sum of the weights of the resin and Boc-amino acid added to the reaction vessel, then add 10 equivalents of benzoyl chloride and 10 equivalents of pyridine to deactivate any unused hydroxymethyl resin. Wash as set forth in steps 15 and 16. Then employ steps 1-18 of Example 6 for remaining protected amino acids.

If the final constant weight is not equal to the sum of the weights of the resin and Boc-amino acid added to the reaction vessel, then repeat steps 10 to end as modified above in this example.

EXAMPLE 12 Synthesis of H₂ -His-D-Trp-Ala-Trp-D-Phe-Arg-NH₂

The procedure set forth in Example 6 can be employed to synthesize the peptide H₂ -His-D-Trp-Ala-Trp-D-Phe-Arg-NH₂ employing the following sequence of amino acids:

Aoc*-Arg(Tos)

Boc-D-Phe

Boc-Trp

Boc-Ala

Boc-D-Trp

Boc-His(Tos)

EXAMPLE 13 Synthesis of H₂ -His-D-Trp-Ala-Trp-D-Phe-Gln-NH₂

The procedure set forth in Example 6 can be employed with one modification to synthesize the peptide H₂ -His-D-Trp-Ala-Trp-D-Phe-Gln-NH₂ employing the following sequence of amino acids:

Boc-Gln-ONP

Boc-D-Phe

Boc-Trp

Boc-Ala

Boc-D-Trp

Boc-His(Tos)

The sole modification was made first in the procedure for coupling Boc-Gln-ONP to the resin. This modification consisted of the omission of step 11 of Example 6 in this one coupling procedure.

EXAMPLE 14 Synthesis of H₂ -His-D-Trp-Ala-Trp-D-Phe-Glu-NH₂

The procedure set forth in Example 6 can be employed to synthesize the peptide H₂ -His-D-Trp-Ala-Trp-D-Phe-Glu-NH₂ employing the following sequence of amino acids:

Boc-Glu-γ-Bzl

Boc-D-Phe

Boc-Trp

Boc-Ala

Boc-D-Trp

Boc-His(Tos)

EXAMPLE 15 Synthesis of H₂ -His-D-Trp-Ala-Trp-D-Phe-HomoArg-NH₂

The procedure set forth in Example 6 can be employed to synthesize the peptide H₂ -His-D-Trp-Ala-Trp-D-Phe-HomoArg-NH₂ employing the following sequence of amino acids:

Boc-HomoArg(Tos)

Boc-D-Phe

Boc-Trp

Boc-Ala

Boc-D-Trp

Boc-His(Tos)

EXAMPLE 16 Synthesis of H₂ -3-N-Me-His-D-Trp-Ala-Trp-D-Phe-Lys-NH₂

The procedure set forth in Example 6 can be employed to synthesize the peptide H₂ -3-N-Me-His-D-Trp-Ala-Trp-D-Phe-Lys-NH₂ employing the following sequence of amino acids:

Boc-Lys(ClZ)

Boc-D-Phe

Boc-Trp

Boc-Ala

Boc-D-Trp

Boc-3-N-Me-His

EXAMPLE 17 Synthesis of H₂ -His-D-Trp-Ala-Trp-D-Phe-Lys-NHCH₂ CH₃

The procedure set forth in Example 6 can be employed with several modifications to synthesize the peptide H₂ -His-D-Trp-D-Ala-Trp-D-Phe-Lys-NHCH₂ CH₃ employing the following sequence of amino acids:

Boc-Lys(ClZ)

Boc-D-Phe

Boc-Trp

Boc-D-Ala

Boc-D-Trp

Boc-His(Tos)

The following ethylamine (CH₃ CH₂ NH₂) cleavage procedure was employed in place of the HF cleavage procedure of Example 6:

After completion of the synthesis of the desired peptide resin, the reaction vessel containing the peptide resin was then placed in a dessicator and dried overnight under a vacuum. The dried peptide resin was removed from the reaction vessel and placed in another vessel suitable for ethylamine cleavage. This latter vessel also contained a magnetic stirring bar. The vessel was placed in an ice bath and gaseous ethylamine was condensed into the vessel. The contents of the vessel was stirred overnight.

This cleavage procedure was then followed by the extraction and purifications procedures as set forth in Example 6.

EXAMPLE 18 Synthesis of H₂ -His-D-Trp-Ala-Trp-D-Phe-Orn-NH₂

The procedure set forth in Example 6 can be employed to synthesize the peptide H₂ -His-D-Trp-Ala-Trp-D-Phe-Orn-NH₂ employing the following sequence of amino acids:

Boc-Orn(Z*)

Boc-D-Phe

Boc-Trp

Boc-Ala

Boc-D-Trp

Boc-His (Tos)

EXAMPLE 19 Synthesis of H₂ -His-D-Trp-Val-Trp-D-Phe-Lys-NH₂

The procedure set forth in Example 6 can be employed to synthesize the peptide H₂ -His-D-Trp-Val-Trp-D-Phe-Lys-NH₂ employing the following sequence of amino acids:

Boc-Lys(ClZ)

Boc-D-Phe

Boc-Trp

Boc-Val

Boc-D-Trp

Boc-His (Tos)

EXAMPLE 20 Synthesis of H₂ -His-D-Trp-Ser-Trp-D-Phe-Lys-NH₂

The procedure set forth in Example 6 can be employed to synthesize the peptide H₂ -His-D-Trp-Ser-Trp-D-Phe-NH₂ employing the following sequence of amino acids:

Boc-Lys(ClZ)

Boc-D-Phe

Boc-Trp

Boc-Ser(Bzl)

Boc-D-Trp

Boc-His (Tos)

EXAMPLE 21 In Vitro Growth Hormone Release Study

Female rats of the CD-1 strain were housed in a constant temperature room at 24° C. with 14 hours light and 10 hours darkness. The rats were fed Purina brand rat chow ab libitum. All studies were started between 0800 and 1000 hours.

Pituitaries were removed from 20 day old female rats. In each polytetrafluoroethylene beaker (10 ml) was incubated two pituitaries at 36° C. in 1 ml of lactated Ringer's solution in a Dubnoff Shaker (90 cycles/min.). Three beakers were employed for each dosage shown in Table VI. All medium in each beaker was removed each hour (e.g., P₁, P₂, I₃, I₄, I₅) and then fresh medium was added back to each beaker. Each medium removed was assayed for GH, in duplicate, by a standard radioimmunoassay (RIA).

The growth hormone agonist of Example 1 was not added to the incubation mediums employed during the first hour of the incubation period (P₁) or to the incubation mediums employed during the second hour of the incubation period (P₂). The growth hormone agonist of Example 1 was dissolved in dimethylsulfoxide (DMSO; 10:1, agonist:DMSO), added to each incubation medium employed during the third hour of the incubation period (I₃), to each medium employed during the fourth hour of the incubation period (I₄), and, when performed, to each medium employed during the fifth hour of the incubation period (I₅). The release of growth hormone was recorded as ΔGH and calculated by subtracting the amount of GH released at P₂ from that released at I₃, I₄, and, when performed, I₅. The agonist activity was determined from the release at I₃, I₄, and, when performed, I₅. The mean of the ΔGH values obtained from the three beakers per dosage level measured at I₃, I₄, and, when performed, I₅ are set forth in Table VI.

EXAMPLE 22 In Vitro Growth Hormone Release Study

The procedure set forth in Example 21 was employed in an in vitro growth hormone release study of the peptide of Example 2 and the results therefrom are set forth in Table VII.

EXAMPLE 23 In Vitro Growth Hormone Release Study

The procedure set forth in Example 21 was employed in an in vitro growth hormone release study of the peptide of Example 3 and the results therefrom are set forth in Table VIII.

EXAMPLE 24 In Vitro Growth Release Study

The procedure set forth in Example 21 was employed in an in vitro growth hormone release study of the peptide of Example 4 and the results therefrom are set forth in Table IX.

EXAMPLE 25 In Vitro Growth Hormone Release Study

The procedure set forth in Example 21 was employed in an in vitro growth hormone release study of the peptide of Example 5 and the results therefrom are set forth in Table X.

EXAMPLE 26 In Vitro Growth Hormone Release Study

The procedure set forth in Example 21 was employed in an in vitro growth hormone release study of the peptide of Example 6 and the results therefrom are set forth in Table XI.

EXAMPLE 27 In Vitro Growth Hormone Release Study

The procedure set forth in Example 21 was employed in an in vitro growth hormone release study of the peptide of Example 7 and the results therefrom are set forth in Table XII.

EXAMPLE 28 In Vitro Growth Hormone Release Study

The procedure set forth in Example 21 was employed in an in vitro growth hormone release study of the peptide of Example 8 and the results therefrom are set forth in Table XIII.

EXAMPLE 29 In Vitro Growth Hormone Release Study

The procedure set forth in Example 21 was employed in an in vitro growth hormone release study of the peptide of Example 9 and the results therefrom are set forth in Table XIV.

EXAMPLE 30 In Vitro Growth Hormone Release Study

The procedure set forth in Example 21 was employed in an in vitro growth hormone release study of the peptide of Example 10 and the results therefrom are set forth in Table XV.

EXAMPLE 31 In Vitro Growth Hormone Release Study

The procedure set forth in Example 21 was employed in an in vitro growth hormone release study of the peptide of Example 11 and the results therefrom are set forth in Table XVI.

EXAMPLE 32 In Vitro Growth Hormone Release Study

The procedure set forth in Example 21 was employed in an in vitro growth hormone release study of the peptide of Example 12 and the results therefrom are set forth in Table XVII.

EXAMPLE 33 In Vitro Growth Hormone Release Study

The procedure set forth in Example 21 was employed in an in vitro growth hormone release study of the peptide of Example 13 and the results therefrom are set forth in Table XVIII.

EXAMPLE 34 In Vitro Growth Hormone Release Study

The procedure set forth in Example 21 was employed in an in vitro growth hormone release study of the peptide of Example 14 and the results therefrom are set forth in Table XIX.

EXAMPLE 35 In Vitro Growth Hormone Release Study

The procedure set forth in Example 21 was employed in an in vitro growth hormone release study of the peptide of Example 15 and the results therefrom are set forth in Table XX.

EXAMPLE 36 In Vitro Growth Hormone Release Study

The procedure set forth in Example 21 was employed in an in vitro growth hormone release study of the peptide of Example 16 and the results therefrom are set forth in Table XXI.

EXAMPLE 37 In Vitro Growth Hormone Release Study

The procedure set forth in Example 21 was employed in an in vitro growth hormone release study of the peptide of Example 17 and the results therefrom are set forth in Table XXII.

EXAMPLE 38 In Vitro Growth Hormone Release Study

The procedure set forth in Example 21 was employed in an in vitro growth hormone release study of the peptide of Example 18 and the results therefrom are set forth in Table XXIII.

EXAMPLE 39 In Vitro Growth Hormone Release Study

The procedure set forth in Example 21 was employed in an in vitro growth hormone release study of the peptide of Example 19 and the results therefrom are set forth in Table XXIV.

EXAMPLE 40 In Vitro Growth Hormone Release Study

The procedure set forth in Example 21 was employed in an in vitro growth hormone release study of the peptide of Example 20 and the results therefrom are set forth in Table XXV.

                  TABLE VI                                                         ______________________________________                                         IN VITRO GROWTH HORMONE RELEASE                                                Dosage.sup.2                     p                                             H.sub.2 -Tyr-D-Trp-Ala-Trp-D-Phe-Met-NH.sub.2                                                        ΔGH.sup.1                                                                           Value.sup.4                                   ______________________________________                                         --                    -148 ± 137                                                                             --                                            30                     456 ± 151                                                                             NS.sup.3                                      300                    1,260 ± 245                                                                           <0.01                                         1,000                  1,832 ± 441                                                                           <0.01                                         ______________________________________                                          .sup.1 The mean of 6 assays given in terms of ng/ml incubation medium .+-      standard error of the mean (SEM)                                               .sup.2 Given in terms of ng/ml incubation medium                               .sup.3 NS denotes not significant                                              .sup.4 Comparison of the GH levels in medium containing growth hormone         agonist analog to the GH levels in medium without the agonist            

                  TABLE VII                                                        ______________________________________                                         IN VITRO GROWTH HORMONE RELEASE                                                Dosage.sup.2                                                                   H.sub.2 -Tyr-D-Trp-Ala-Trp-D-Phe-Thr-NH.sub.2                                                       ΔGH.sup.1                                                                           p Value.sup.4                                  ______________________________________                                         --                   -40 ± 35                                                                               --                                             10                   94 ± 69 NS.sup.3                                       100                  650 ± 320                                                                              NS.sup.11                                      1,000                2,167 ± 591                                                                            <0.01                                          10,000               2,957 ± 834                                                                            <0.01                                          ______________________________________                                          .sup.1 The mean of 6 assays given in terms of ng/ml incubation medium .+-      standard error of the mean (SEM)                                               .sup.2 Given in terms of ng/ml incubation medium                               .sup.3 NS denotes not significant                                              .sup.4 Comparison of the GH levels in medium containing growth hormone         agonist analog to the GH levels in medium without the agonist            

                  TABLE VIII                                                       ______________________________________                                         IN VITRO GROWTH HORMONE RELEASE                                                Dosage.sup.2                                                                   H.sub.2 -Tyr-D-Trp-Ala-Trp-D-Phe-Gln-OH                                                             ΔGH.sup.1                                                                           p Value.sup.4                                  ______________________________________                                         --                   -40 ± 35                                                                               --                                             100                  753 ± 559                                                                              NS.sup.3                                       1,000                2,759 ± 515                                                                            <0.001                                         10,000               3,994 ± 1,214                                                                          <0.01                                          ______________________________________                                          .sup.1 The mean of 6 assays given in terms of ng/ml incubation medium .+-      standard error of the mean (SEM)                                               .sup.2 Given in terms of ng/ml incubation medium                               .sup.3 NS denotes not significant                                              .sup.4 Comparison of the GH levels in medium containing growth hormone         agonist analog to the GH levels in medium without the agonist            

                  TABLE IX                                                         ______________________________________                                         IN VITRO GROWTH HORMONE RELEASE                                                Dosage.sup.2                                                                   H.sub.2 -Tyr-D-Trp-Ala-Trp-D-Phe-Gln-NH.sub.2                                                       .increment.GH.sup.1                                                                       p Value.sup.4                                  ______________________________________                                         --                    -40 ±  35                                                                             --                                                10                  240 ± NS.sup.3                                         100                2,000 ± 523                                                                            <0.01                                           1,000               4,235 ± 785                                                                            <0.001                                         10,000               4,141 ± 576                                                                            <0.001                                         ______________________________________                                          .sup.1 The mean of 6 assays given in terms of ng/ml incubation medium .+-      standard error of the mean (SEM)                                               .sup.2 Given in terms of ng/ml incubation                                      .sup.3 NS denotes not significant                                              .sup.4 Comparison of the GH levels in medium containing growth hormone         agonist analog to the GH levels in medium without the agonist            

                  TABLE X                                                          ______________________________________                                         IN VITRO GROWTH HORMONE RELEASE                                                Dosage.sup.2                                                                   H.sub.2 -Tyr-D-Trp-Ala-Trp-D-Phe-Asn-NH.sub.2                                                       .increment.GH.sup.1                                                                       p Value.sup.3                                  ______________________________________                                         --                    -89 ±  51                                                                             --                                               30                   244 ± <0.01                                            100                  528 ± 184                                                                            <0.01                                          1,000                1,670 ± 126                                                                             <0.001                                        ______________________________________                                          .sup.1 The mean of 6 assays given in terms of ng/ml incubation medium .+-      standard error of the mean (SEM)                                               .sup.2 Given in terms of ng/ml incubation                                      .sup.3 Comparison of the GH levels in medium containing growth hormone         agonist analog to the GH levels in medium without the agonist            

                  TABLE XI                                                         ______________________________________                                         IN VITRO GROWTH HORMONE RELEASE                                                Dosage.sup.2                                                                   H.sub.2 -His-D-Trp-Ala-Trp-D-Phe-Lys-NH.sub.2                                                       .increment.GH.sup.1                                                                       p Value.sup.3                                  ______________________________________                                         --                    -167 ± 114                                                                            --                                              1                     955 ± 272                                                                            <0.01                                           3                   1,603 ± 305                                                                            <0.001                                         10                   2,244 ± 173                                                                            <0.001                                         30                   2,198 ± 358                                                                            <0.001                                         ______________________________________                                          .sup.1 The mean of 9 assays given in terms of ng/ml incubation medium .+-      standard error of the mean (SEM)                                               .sup.2 Given in terms of ng/ml incubation                                      .sup.3 Comparison of the GH levels in medium containing growth hormone         agonist analog to the GH levels in medium without the agonist            

                  TABLE XII                                                        ______________________________________                                         IN VITRO GROWTH HORMONE RELEASE                                                Dosage.sup.2                                                                   H.sub.2 -Tyr-D-Trp-Ala-Trp-D-Phe-Lys-NH.sub.2                                                       .increment.GH.sup.1                                                                       p Value.sup.3                                  ______________________________________                                         --                    -29 ±  59                                                                             --                                                30                1,346 ± 328                                                                            <0.001                                           300                2,160 ± 166                                                                            <0.001                                          3,000               1,630 ± 135                                                                            <0.001                                         30,000               1,318 ± 247                                                                            <0.001                                         ______________________________________                                          .sup.1 The mean of 9 assays given in terms of ng/ml incubation medium .+-      standard error of the mean (SEM)                                               .sup.2 Given in terms of ng/ml incubation                                      .sup.3 Comparison of the GH levels in medium containing growth hormone         agonist analog to the GH levels in medium without the agonist            

                  TABLE XIII                                                       ______________________________________                                         IN VITRO GROWTH HORMONE RELEASE                                                Dosage.sup.2                                                                   H.sub.2 -Tyr-D-Trp-Ala-Trp-D-Phe-Glu-NH.sub.2                                                       .increment.GH.sup.1                                                                       p Value.sup.3                                  ______________________________________                                         --                    -29 ±  59                                                                             --                                                30                  224 ± ˜0.05                                      300                  472 ± 104                                                                            ˜0.05                                     3,000               1,404 ± 179                                                                            <0.001                                         30,000               1,909 ± 270                                                                            <0.001                                         ______________________________________                                          .sup.1 The mean of 9 assays given in terms of ng/ml incubation medium .+-      standard error of the mean (SEM)                                               .sup.2 Given in terms of ng/ml incubation                                      .sup.3 Comparison of the GH levels in medium containing growth hormone         agonist analog to the GH levels in medium without the agonist            

                  TABLE XIV                                                        ______________________________________                                         IN VITRO GROWTH HORMONE RELEASE                                                Dosage.sup.2                                                                   H.sub.2 -Tyr-D-Trp-Ala-Trp-D-Phe-Phe-NH.sub.2                                                       .increment.GH.sup.1                                                                       p Value.sup.4                                  ______________________________________                                         --                     29 ± 164                                                                             --                                                30                  10 ±  57                                                                             .sup. NS.sup.3                                   300                  330 ± NS3                                             3,000                 710 ± ˜0.01                                    30,000               1,484 ± 135                                                                            <0.001                                         ______________________________________                                          .sup.1 The mean of 9 assays given in terms of ng/ml incubation medium .+-      standard error of the mean (SEM)                                               .sup.2 Given in terms of ng/ml incubation                                      .sup.3 NS denotes not significant                                              .sup.4 Comparison of the GH levels in medium containing growth hormone         agonist analog to the GH levels in medium without the agonist            

                  TABLE XV                                                         ______________________________________                                         IN VITRO GROWTH HORMONE RELEASE                                                Dosage .sup.2                    p                                             H.sub.2 -Tyr-D-Trp-Gly-Trp-D-Phe-Gln-NH.sub.2                                                        .increment.GH.sup.1                                                                       Value.sup.4                                   ______________________________________                                         --                    -89 ±  50                                                                             --                                               30                   103 ± 248                                                                            NS.sup.3                                         100                  167 ± <0.02                                          1,000                1,092 ± <0.001                                         ______________________________________                                          .sup.1 The mean of 6 assays given in terms of ng/ml incubation medium .+-      standard error of the mean (SEM)                                               .sup.2 Given in terms of ng/ml incubation                                      .sup.3 NS denotes not significant                                              .sup.4 Comparison of the GH levels in medium containing growth hormone         agonist analog to the GH levels in medium without the agonist            

                  TABLE XVI                                                        ______________________________________                                         IN VITRO GROWTH HORMONE RELEASE                                                Dosage .sup.2                                                                  H.sub.2 -His-D-Trp-Ala-Trp-D-Phe-Lys-OH                                                             .increment.GH.sup.1                                                                       p Value.sup.3                                  ______________________________________                                         --                   -146 ±  67                                                                             --                                              1                     467 ± 178                                                                            <0.01                                           10                    330 ± 167                                                                            <0.02                                          100                  2,441 ± 353                                                                            <0.001                                         ______________________________________                                          .sup.1 The mean of 9 assays given in terms of ng/ml incubation medium .+-      standard error of the mean (SEM)                                               .sup.2 Given in terms of ng/ml incubation                                      .sup.3 Comparison of the GH levels in medium containing growth hormone         agonist analog to the GH levels in medium without the agonist            

                  TABLE XVII                                                       ______________________________________                                         IN VITRO GROWTH HORMONE RELEASE                                                Dosage.sup.2                                                                   H.sub.2 -His-D-Trp-Ala-Trp-D-Phe-Arg-NH.sub.2                                                       .increment.GH.sup.1                                                                       p Value.sup.3                                  ______________________________________                                         --                    -88 ± 56                                                                              --                                              1                     805 ± 152                                                                            <0.001                                          3                     997 ± 249                                                                            <0.001                                         10                   2,064 ± 346                                                                            <0.001                                         ______________________________________                                          .sup.1 The mean of 9 assays given in terms of ng/ml incubation medium .+-      standard error of the mean (SEM).sup.2 Given in terms of ng/ml incubation      medium                                                                         .sup.3 Comparison of the GH levels in medium containing growth hormone         agonist analog to the GH levels in medium without the agonist            

                  TABLE XVIII                                                      ______________________________________                                         IN VITRO GROWTH HORMONE RELEASE                                                Dosage.sup.2                                                                   H.sub.2 -His-D-Trp-Ala-Trp-D-Phe-Gln-NH.sub.2                                                       .increment.GH.sup.1                                                                       p Value.sup.4                                  ______________________________________                                         --                   -288 ± 182                                                                             --                                              1                     5 ± 136                                                                              .sup. NS.sup.3                                  3                    140 ± 168                                                                             NS                                             10                    275 ±  66                                                                             ˜0.02                                    ______________________________________                                          .sup.1 The mean of 6 assays given in terms of ng/ml incubation medium .+-      standard error of the mean (SEM)                                               .sup.2 Given in terms of ng/ml incubation                                      .sup.3 NS denotes not significant                                              .sup.4 Comparison of the GH levels in medium containing growth hormone         agonist analog to the GH levels in medium without the agonist            

                  TABLE XIX                                                        ______________________________________                                         IN VITRO GROWTH HORMONE RELEASE                                                Dosage.sup.2                                                                   H.sub.2 -His-D-Trp-Ala-Trp-D-Phe-Glu-NH.sub.2                                                       .increment.GH.sup.1                                                                       p Value.sup.4                                  ______________________________________                                         --                    -251 ± 105                                                                            --                                              1                    -78 ± 72                                                                              .sup. NS.sup.3                                  3                   -294 ± 75                                                                              NS                                             10                   -243 ± 71                                                                              NS                                             30                    117 ± 41                                                                              <0.01                                          ______________________________________                                          .sup.1 The mean of 9 assays given in terms of ng/ml incubation medium .+-      standard error of the mean (SEM)                                               .sup.2 Given in terms of ng/ml incubation                                      .sup.3 NS denotes not significant                                              .sup.4 Comparison of the GH levels in medium containing growth hormone         agonist analog to the GH levels in medium without the agonist            

                  TABLE XX                                                         ______________________________________                                         IN VITRO GROWTH HORMONE RELEASE                                                Dosage.sup.2                                                                   H.sub.2 -His-D-Trp-Ala-Trp-D-Phe-HomoArg-NH.sub.2                                                      .increment.GH.sup.1                                                                    p Value.sup.3                                  ______________________________________                                         --                   -553 ± 105                                                                             --                                              1                   -150 ± 124                                                                             <0.02                                          10                    1,096 ± 341                                                                           <0.001                                         ______________________________________                                          .sup.1 The mean of 6 assays given in terms of ng/ml incubation medium .+-      standard error of the mean (SEM)                                               .sup.2 Given in terms of ng/ml incubation                                      .sup.3 Comparison of the GH levels in medium containing growth hormone         agonist analog to the GH levels in medium without the agonist            

                  TABLE XXI                                                        ______________________________________                                         IN VITRO GROWTH HORMONE RELEASE                                                Dosage.sup.2                                                                   H.sub.2 -3-N-Me-D-Trp-Ala-Trp-D-Phe-Lys-NH.sub.2                                                      .increment.GH.sup.1                                                                    p Value.sup.4                                   ______________________________________                                         --                    435 ± 176                                                                            --                                               1                    165 ± 136                                                                            NS.sup.3                                        10                  1,857 ± 254                                                                            <0.01                                           ______________________________________                                          .sup.1 The mean of 9 assays given in terms of ng/ml incubation medium .+-      standard error of the mean (SEM)                                               .sup.2 Given in terms of ng/ml incubation                                      .sup.3 NS denotes not significant                                              .sup.4 Comparison of the GH levels in medium containing growth hormone         agonist analog to the GH levels in medium without the agonist            

                                      TABLE XXII                                   __________________________________________________________________________     IN VITRO GROWTH HORMONE RELEASE                                                Dosage.sup.2                                                                   H.sub.2 --His--D-Trp--Ala--Trp--D-Phe--Lys--NHCH.sub.2 CH.sub.3                                           ΔGH.sup.1                                                                       p Value.sup.4                                __________________________________________________________________________     --                         435 ± 176                                                                          --                                            1                         726 ± 115                                                                          NS.sup.3                                     10                         1,688 ± 300                                                                        <0.01                                        __________________________________________________________________________      .sup.1 The mean of 9 assays given in terms of ng/ml incubation medium .+-      standard error of the mean (SEM)                                               .sup.2 Given in terms of ng/ml incubation medium                               .sup.3 NS denotes not significant                                              .sup.4 Comparison of the GH levels in medium containing growth hormone         agonist analog to the GH levels in medium without the agonist            

                                      TABLE XXIII                                  __________________________________________________________________________     IN VITRO GROWTH HORMONE RELEASE                                                Dosage.sup.2                                                                   H.sub.2 --His--D-Trp--Ala--Trp--D-Phe--Orn--NH.sub.2                                                   ΔGH.sup.1                                                                        p Value.sup.4                                  __________________________________________________________________________     --                       -553 ± 105                                                                         --                                              1                      -295 ±  93                                                                          NS.sup.3                                       10                       356 ±  92                                                                          <0.001                                         __________________________________________________________________________      .sup.1 The mean of 6 assays given in terms of ng/ml incubation medium .+-      standard error of the mean (SEM)                                               .sup.2 Given in terms of ng/ml incubation medium                               .sup.3 NS denotes not significant                                              .sup.4 Comparison of the GH levels in medium containing growth hormone         agonist analog to the GH levels in medium without the agonist            

                                      TABLE XXIV                                   __________________________________________________________________________     IN VITRO GROWTH HORMONE RELEASE                                                Dosage.sup.2                                                                   H.sub.2 --His--D-Trp--Val--Trp--D-Phe--Lys--NH.sub.2                                                   ΔGH.sup.1                                                                        p Value.sup.3                                  __________________________________________________________________________     --                       -553 ± 105                                                                         --                                             30                      -118 ±  65                                                                          <0.01                                          __________________________________________________________________________      .sup.1 The mean of 6 assays given in terms of ng/ml incubation medium .+-      standard error of the mean (SEM)                                               .sup.2 Given in terms of ng/ml incubation medium                               .sup.3 Comparison of the GH levels in medium containing growth hormone         agonist analog to the GH levels in medium without the agonist            

                                      TABLE XXV                                    __________________________________________________________________________     IN VITRO GROWTH HORMONE RELEASE                                                Dosage.sup.2                                                                   H.sub.2 --His--D-Trp--Ser--Trp--D-Phe--Lys--NH.sub.2                                                   ΔGH.sup.1                                                                        p Value.sup.4                                  __________________________________________________________________________     --                      -125 ± 132                                                                          --                                             10                      161 ± 157                                                                           NS.sup.3                                       30                      705 ± 149                                                                           <0.01                                          __________________________________________________________________________      .sup.1 The mean of 6 assays given in terms of ng/ml incubation medium .+-      standard error of the mean (SEM)                                               .sup.2 Given in terms of ng/ml incubation medium                               .sup.3 NS denotes not significant                                              .sup.4 Comparison of the GH levels in medium containing growth hormone         agonist analog to the GH levels in medium without the agonist            

The results set forth in Tables VI-XXV demonstrate that peptides within the scope of the instant invention can induce a significant in vitro release of growth hormone from the pituitary.

By introducing various other hormones, e.g., somatostatin, testosterone, cortisol, insulin, etc., into the incubation medium of Examples 11-20, one can study what effect these latter hormones have on the regulation of growth hormone secretion.

EXAMPLE 41 In Vivo Growth Hormone Release Study

Female rats of The CD-1 strain were housed in a constant temperature room at 24° C. with 14 hours light and 10 hours darkness. The rats were fed Purina brand rat chow ab libitum. All studies were started between 0800 and 1000 hours.

Each female rat (21 days old; eight rats per dosage level shown in Table XXVI) was injected subcutaneously with a desired dosage of the peptide of Example 6. Approximately 15 minutes after injection, the rat was guillotined. A blood sample was collected from the guillotined rat. The blood sample was centrifuged and a serum sample was collected therefrom. Each serum sample was assayed for GH, in duplicate, by a standard radioimmunoassay (RIA). The mean of the GH values obtained per dosage level are set forth in Table XXVI.

EXAMPLE 42 In Vivo Growth Hormone Release Study

The procedure set forth in Example 41 was employed in an in vivo growth hormone release study of the peptide of Example 11 and the results thereform are set forth in Table XXVII.

EXAMPLE 43 In Vivo Growth Hormone Release Study

The procedure set forth in Example 41 was employed in an in vivo growth hormone release study of the peptide of Example 12 and the results therefrom are set forth in Table XXVIII.

EXAMPLE 44 In Vivo Growth Hormone Release Study

The procedure set forth in Example 41 was employed in an in vivo growth hormone release study of the peptide of Example 13 and the results therefrom are set forth in Table XXIX.

EXAMPLE 45 In Vivo Growth Hormone Release Study

The procedure set forth in Example 41 was employed in an in vivo growth hormone release study of the peptide of Example 14 and the results therefrom are set forth in Table XXX.

EXAMPLE 46 In Vivo Growth Hormone Release Study

The procedure set forth in Example 41 was employed in an in vivo growth hormone release study of the peptide of Example 15 and the results therefrom are set forth in Table XXXI.

EXAMPLE 47 In Vivo Growth Hormone Release Study

The procedure set forth in Example 41 was employed in an in vivo growth hormone release study of the peptide of Example 16 and the results therefrom are set forth in Table XXXII.

EXAMPLE 48 In Vivo Growth Hormone Release Study

The procedure set forth in Example 41 was employed in an in vivo growth hormone release study of the peptide of Example 17 and the results therefrom are set forth in Table XXXIII.

                                      TABLE XXVI                                   __________________________________________________________________________     IN VIVO GROWTH HORMONE RELEASE                                                 Dosage.sup.2                                                                   H.sub.2 --His--D-Trp--Ala--Trp--D-Phe--Lys--NH.sub.2                                                    ΔGH.sup.1                                                                      p Value.sup.4                                   __________________________________________________________________________     Control                   0 ±  0                                                                           --                                              0.3                       6 ±  4                                                                           NS.sup.3                                        1.0                      36 ± 15                                                                           <0.04                                           3.0                      66 ± 15                                                                           ˜0.001                                    10.0                     100 ± 19                                                                          <0.001                                          30.0                     122 ±  4                                                                          <0.001                                          __________________________________________________________________________      .sup.1 The mean of 6 assays given in terms of ng/ml subcutaneous ±          standard error of the mean (SEM)                                               .sup.2 Given in terms of μg/ml serum                                        .sup.3 NS denotes not significant                                              .sup.4 GH levels in serum of rats subcutaneously injected with peptide         compared to the GH levels in serum of control rats                       

                                      TABLE XXVII                                  __________________________________________________________________________     IN VIVO GROWTH HORMONE RELEASE                                                 Dosage.sup.2                                                                   H.sub.2 --His--D-Trp--Ala--Trp--D-Phe--Lys--OH                                                         ΔGH.sup.1                                                                       p Value.sup.3                                   __________________________________________________________________________     Control                  1.7 ±  1                                                                          --                                               3.0                     76   ± 24                                                                         <0.01                                           10.0                    119   ± 25                                                                         <0.001                                          30.0                    226   ± 43                                                                         <0.001                                          __________________________________________________________________________      .sup.1 The mean of 8 assays given in terms of ng/ml subcutaneous ±          standard error of the mean (SEM)                                               .sup.2 Given in terms of μg/ml serum                                        .sup.3 GH levels in serum of rats subcutaneously injected with peptide         compared to the GH levels in serum of control rats                       

                                      TABLE XXVIII                                 __________________________________________________________________________     IN VIVO GROWTH HORMONE RELEASE                                                 Dosage.sup.2                                                                   H.sub.2 --His--D-Trp--Ala--Trp--D-Phe--Arg--NH.sub.2                                                   ΔGH.sup.1                                                                        p Value.sup.4                                  __________________________________________________________________________     Control                 5.7 ±  2.2                                                                          --                                             1.0                     9.2 ±  3.4                                                                          NS.sup.3                                       3.0                     32.2 ±  5.5                                                                         <0.001                                         10.0                    87.5 ± 31                                                                            0.02                                          30.0                    31.1 ±  3.4                                                                         <0.001                                         __________________________________________________________________________      .sup.1 The mean of 8 assays given in terms of ng/ml subcutaneous ±          standard error of the mean (SEM)                                               .sup.2 Given in terms of μg/ml serum                                        .sup.3 NS denotes not significant                                              .sup.4 GH levels in serum of rats subcutaneously injected with peptide         compared to the GH levels in serum of control rats                       

                                      TABLE XXIX                                   __________________________________________________________________________     IN VIVO GROWTH HORMONE RELEASE                                                 Dosage.sup.2                                                                   H.sub.2 --His--D-Trp--Ala--Trp--D-Phe--Gln--NH.sub.2                                                   ΔGH.sup.1                                                                      p Value.sup.4                                    __________________________________________________________________________     Control                 4.9 ± 0.9                                                                         --                                               1.0                     1.4 ± 0.9                                                                         NS.sup.3                                         3.0                     3.8 ± 2.1                                                                         NS                                               10.0                    32.1 ± 11.4                                                                       <0.05                                            __________________________________________________________________________      .sup.1 The mean of 9 assays given in terms of ng/ml subcutaneous ±          standard error of the mean (SEM)                                               .sup.2 Given in terms of μg/ml serum                                        .sup.3 NS denotes not significant                                              .sup.4 GH levels in serum of rats subcutaneously injected with peptide         compared to the GH levels in serum of control rats                       

                                      TABLE XXX                                    __________________________________________________________________________     IN VIVO GROWTH HORMONE RELEASE                                                 Dosage.sup.2                                                                   H.sub.2 --His--D-Trp--Ala--Trp--D-Phe--Glu--NH.sub.2                                                   ΔGH.sup.1                                                                      p Value.sup.4                                    __________________________________________________________________________     Control                 0.34 ± 0.19                                                                       --                                               1.0                     0.10 ± 0                                                                          NS.sup.3                                         3.0                     1.50 ± 0.56                                                                       NS                                               10.0                    1.4 ± 0.78                                                                        NS                                               30.0                    8.06 ± 2.68                                                                       ˜0.01                                      __________________________________________________________________________      .sup.1 The assays given in terms of ng/ml subcutaneous ± standard erro      of the mean (SEM)                                                              .sup.2 Given in terms of μg/ml serum                                        .sup.3 NS denotes not significant                                              .sup.4 GH levels in serum of rats subcutaneously injected with peptide         compared to the GH levels in serum of control rats                       

                                      TABLE XXXI                                   __________________________________________________________________________     IN VIVO GROWTH HORMONE RELEASE                                                 Dosage.sup.2                                                                   H.sub.2 --His--D-Trp--Ala--Trp--D-Phe--HomoArg--NH.sub.2                                                  ΔGH.sup.1                                                                     p Value.sup.4                                  __________________________________________________________________________     Control                    0 ± 0                                                                            --                                             0.3                        3 ± 2                                                                            NS.sup.3                                       10.0                       62 ± 8                                                                           <0.001                                         __________________________________________________________________________      .sup.1 The mean of 6 assays given in terms of ng/ml subcutaneous ±          standard error of the mean (SEM)                                               .sup.2 Given in terms of μg/ml serum                                        .sup.3 NS denotes not significant                                              .sup.4 GH levels in serum of rats subcutaneously injected with peptide         compared to the GH levels in serum of control rats                       

                                      TABLE XXXII                                  __________________________________________________________________________     IN VIVO GROWTH HORMONE RELEASE                                                 Dosage.sup.2                                                                   H.sub.2 --3-N--Me--His--D-Trp--Ala--Trp--D-Phe--Lys--NH.sub.2                                               ΔGH.sup.1                                                                      p Value.sup.3                               __________________________________________________________________________     Control                      1.1 ± 0.6                                                                         --                                           0.3                         45.0 ± 10                                                                         ˜0.001                                10.0                         128 ± 16                                                                          <0.001                                      __________________________________________________________________________      .sup.1 The mean of 6 assays given in terms of ng/ml subcutaneous ±          standard error of the mean (SEM)                                               .sup.2 Given in terms of μg/ml serum                                        .sup.3 GH levels in serum of rats subcutaneously injected with peptide         compared to the GH levels in serum of control rats                       

                                      TABLE XXXIII                                 __________________________________________________________________________     IN VIVO GROWTH HORMONE RELEASE                                                 Dosage.sup.2                                                                   H.sub.2 --His--D-Trp--Ala--Trp--D-Phe--Lys--NHCH.sub.2 CH.sub.3                                           ΔGH.sup.1                                                                      p Value.sup.3                                 __________________________________________________________________________     Control                    1.1 ± 0.6                                                                         --                                             0.3                       13.0 ± 5                                                                          <0.05                                         10.0                       119 ± 12                                                                          <0.001                                        __________________________________________________________________________      .sup.1 The mean of 6 assays given in terms of ng/ml subcutaneous ±          standard error of the mean (SEM)                                               .sup.2 Given in terms of μg/ml serum                                        .sup.3 GH levels in serum of rats subcutaneously injected with peptide         compared to the GH levels in serum of control rats                       

The results set forth in Tables XXVI-XXXIII demonstrate that some peptides within the scope of this invention can induce a significant in vivo release of growth hormone.

Based on this disclosure, many other modifications and ramifications will naturally suggest themselves to those skilled in the art. These are intended to be comprehended as within the scope of this invention. 

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
 1. A peptide having a formula ##STR72## wherein X₁, X₂, and X₃ are selected from a group consisting of --R, --OR, RC(O)-- wherein R is selected from a group consisting of hydrogen and straight chain and branched chain alkyl groups containing 1-6 carbon atoms;a and b are 0 or 1, provided that a and b are 0 when A₁ is a desamino residue; A₁ and A₄ are selected from a group consisting of His, Arg, Lys, α-Naphth, β-Naphth, IQl, Tyr, Trp, Phe, homologues and analogues thereof, and, with respect to A₁, the desamino forms thereof; A₂ and A₅ are selected from a group consisting of D-His, D-Arg, D-Lys, D-α-Naphth, D-β-Naphth, D-Iql, D-Tyr, D-Trp, D-Phe, and homologues and analogues thereof; A₃ is selected from a group consisting of Gly, Ala, Val, Leu, Ile, Pro, Ser, Thr, Met, Asp, Glu, Asn, Gln, His, D-Ala, D-Val, D-Leu, D-Ile, D-Pro, D-Ser, D-Thr, D-Met, D-Asp, D-Glu, D-Asn, D-Gln, D-His, and homologues and analogues thereof; A₆ is selected from a group consisting of amino acids of the L- and D-configuration, homologues and analogues thereof, and the descarboxy forms thereof; and Y is selected from a group consisting of C-terminal and descarboxy alpha-carbon substitutions; and the pharmaceutically acceptable salts thereof.
 2. The peptide of claim 1 wherein:a is 0 or 1 and b is 0; A₁ and A₄ are selected from the group consisting of His, Tyr, Trp, Phe, homologues and analogues thereof, and with respect to A₁, the desamino forms thereof; A₂ and A₅ are selected from the group consisting of D-His, D-Tyr, D-Trp, D-Phe, and homologues and analogues thereof; A₃ is selected from the group consisting of Gly, Ala, Ser, Asn, Pro, D-Ala, D-Ser, D-Asn, D-Pro, and homologues and analogues thereof; A₆ is selected from the group consisting of Arg, Lys, Orn, His, Asp, Glu, Asn, Gln, D-Arg, D-Lys, D-Orn, D-His, D-Asp, D-Glu, D-Asn, D-Gln, D-Arg, homologues and analogues thereof, and descarboxy forms thereof; Y is selected from the group consisting of --CH₂ OH, --OR, and --NR₁ R₂, wherein R, R₁ and R₂ are selected from the group consisting of hydrogen and straight and branched chain alkyl groups containing 1-6 carbon atoms; and the pharmaceutically acceptable salts thereof.
 3. The peptide of claim 1 having the formula ##STR73## wherein a is 0 or 1;X₂ is selected from the group consisting of RCO and R-- wherein R is selected from the group consisting of hydrogen and alkyl groups containing 1-2 carbon atoms; A₁ is selected from the group consisting of Tyr, O-Me-Tyr, His, 3-N-Me-His, p-Cl-Phe, and the desamino forms thereof; A₃ is selected from the group consisting of Ala, Ser, and D-Ala; A₄ is selected from the group consisting of Trp and Tyr; A₅ is selected from the group consisting of D-Phe, D-His, D-Tyr, and D-p-Cl-Phe; A₆ is selected from the group consisting of Arg, HomoArg, Lys, Orn, Asp, Glu, Asn, Gln, and D-Lys; Y is selected from the group consisting of --OR, and --NHR, wherein R is selected from the group consisting of hydrogen and alkyl groups containing 1-2 carbon atoms; and the pharmaceutically acceptable salts thereof.
 4. The peptide of claim 1 of the formulaH₂ -Tyr-D-Trp-Ala-Trp-D-Phe-Met-NH₂.
 5. The peptide of claim 1 of the formulaH₂ -Tyr-D-Trp-Ala-Trp-D-Phe-Thr-NH₂.
 6. The peptide of claim 1 of the formulaH₂ -Tyr-D-Trp-Ala-Trp-D-Phe-Gln-OH.
 7. The peptide of claim 1 of the formulaH₂ -Tyr-D-Trp-ALa-Trp-D-Phe-Gln-NH₂.
 8. The peptide of claim 1 of the formulaH₂ -Tyr-D-Trp-Ala-Trp-D-Phe-Asn-NH₂.
 9. The peptide of claim 1 of the formulaH₂ -His-D-Trp-Ala-Trp-D-Phe-Lys-NH₂.
 10. The peptide of claim 1 of the formulaH₂ -Tyr-Phe-D-Trp-Ala-Trp-D-Phe-Lys-NH₂.
 11. The peptide of claim 1 of the formulaH₂ -Tyr-D-Trp-Ala-Trp-D-Phe-Glu-NH₂.
 12. The peptide of claim 1 of the formulaH₂ -Tyr-D-Trp-Ala-Trp-D-Phe-Phe-NH₂.
 13. The peptide of claim 1 of the formulaH₂ -Tyr-D-Trp-Ala-Trp-D-Phe-Gln-NH₂.
 14. The peptide of claim 1 of the formulaH₂ -His-D-Trp-Ala-Trp-D-Phe-Lys-OH.
 15. The peptide of claim 1 of the formulaH₂ -His-D-Trp-Ala-Trp-D-Phe-Arg-NH₂.
 16. The peptide of claim 1 of the formulaH₂ -His-D-Trp-Ala-Trp-D-Phe-Gln-NH₂.
 17. The peptide of claim 1 of the formulaH₂ -His-D-Trp-Ala-Trp-D-Phe-Glu-NH₂.
 18. The peptide of claim 1 of the formulaH₂ -His-D-Trp-Ala-Trp-D-Phe-HomoArg-NH₂.
 19. The peptide of claim 1 of the formulaH₂ -3-N-Me-His-D-Trp-Ala-Trp-D-Phe-Lys-NH₂.
 20. The peptide of claim 1 of the formulaH₂ -His-D-Trp-ALa-Trp-D-Phe-Lys-NHCH₂ CH₃.
 21. The peptide of claim 1 of the formulaH₂ -His-D-Trp-Ala-Trp-D-Phe-Orn-NH₂.
 22. The peptide of claim 1 of the formulaH₂ -His-D-Trp-Val-Trp-D-Phe-Lys-NH₂.
 23. The peptide of claim 1 of the formulaH₂ -His-D-Trp-Ser-Trp-D-Phe-Lys-NH₂.
 24. A method of releasing growth hormone from a pituitary comprising contacting said pituitary with the peptide of claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, or
 23. 25. A method of releasing growth hormone in vivo from a pituitary comprising contacting said pituitary with the peptide of claim 9, 14, 15, 16, 17, 18, 19, or
 20. 26. An intermediate composition having a formula selected from a group consisting of ##STR74##

    B.sub.1 -B.sub.2 -B.sub.3 -B.sub.4 -B.sub.5 -B'.sub.6 -Y   (VI)

wherein Pr₁ is an α-amino acid protecting group; a, b, m, q, r, and s are each 0 or 1; X'₁, X'₂, and X'₃ are selected from a group consisting of --R, --OR, RC(O)-- wherein R is selected from the group consisting of hydrogen and straight chain and branched chain alkyl groups containing 1-6 carbon atoms; B₁ and B₄ are selected from a group consisting of His, Arg, Lys, α-Naphth, β-Naphth, Igl, Tyr, Trp, Phe, homologues and analogues thereof, the side-chain protected forms thereof, and, with respect to B₁, the desamino forms thereof; B₂ and B₅ are selected from a group consisting of D-His, D-Arg, D-Lys, D-α-Naphth, D-β-Naphth, D-Igl, D-Tyr, D-Trp, D-Phe, homologues and analogues thereof, and the side-chain protected forms thereof; B₃ is selected from a group consisting of amino acids of the L- and D-configurations, homologues and analogues thereof, the side-chain protected forms thereof, and, with respect to B'₆, the descarboxy forms thereof; ® is a resin; Y is selected from a group consisting of C-terminal and descarboxy alpha-carbon substitutions; and Pr₂ is a carboxyl protecting group.
 27. The intermediate composition of claim 26 wherein:B₁ and B₄ are selected from the group consisting of His, Tyr, Trp, Phe, homologues and analogues thereof, and, with respect to B₁, the desamino forms thereof, and the side-chain protected forms thereof; B₂ and B₅ are selected from the group consisting of D-His, D-Tyr, D-Trp, D-Phe, homologues and analogues thereof, and the side-chain protected forms thereof; B₃ is selected from the group consisting of Gly, Ala, Ser, Asn, Pro, D-Ala, D-Ser, D-Asn, D-Pro, homologues and analogues thereof, and the side-chain protected forms thereof; and B₆ and B'₆ are selected from the group consisting of Arg, Lys, Orn, His, Asp, Glu, Asn, Gln, D-Arg, D-Lys, D-Orn, D-His, D-Asp, D-Glu, D-Asn, D-Gln, homologues and analogues thereof, and, with respect to B'₆, the descarboxy forms thereof, and the side-chain protected forms thereof.
 28. The intermediate composition of claim 26 having the formula selected from the group consisting of ##STR75##

    B.sub.1 -D-Trp-B.sub.3 -B.sub.4 -B.sub.5 -B'.sub.6 -Y      (VI)

wherein B₁ is selected from the group consisting of Tyr, O-Me-Tyr, His, 3-N-Me-His, p-Cl-Phe, the desamino forms thereof, and the side-chain protected forms thereof; B₃ is selected from the group consisting of Ala, Ser, D-Ala, and the side-chain protected forms thereof; B₄ is selected from the group consisting of Trp, Tyr, and the side-chain protected forms thereof; B₅ is selected from the group consisting of D-Phe, D-His, D-Tyr, D-p-Cl-Phe, and the side-chain protected forms thereof; and B₆ and B'₆ are selected from the group consisting of Arg, HomoArg, Lys, Orn, Asp, Glu, Asn, Gln, D-Lys, the descarboxy forms thereof, and the side-chain protected forms thereof.
 29. The intermediate composition of claim 26 of the formula

    Boc-Tyr(Brz)-D-Trp-Ala-Trp-D-Phe-Met-®

wherein Brz is o-bromobenzyloxycarbonyl; Boc is t-butyloxycarbonyl; and ® is p-methylbenzhydrylamine resin.
 30. The intermediate composition of claim 26 of the formula

    Boc-Tyr(BrZ)-D-Trp-Ala-Trp-D-Phe-Thr(Bzl)-®

wherein Bzl is benzyl BrZ is p-bromobenzyloxycarbonyl; Boc is t-Butyloxycarbonyl; and ® is p-methylbenzhydrylamine resin.
 31. The intermediate composition of claim 26 of the formula

    Boc-Tyr(BrZ)-D-Trp-Ala-Trp-D-Phe-Glu-α-benzyl ester-®

wherein BrZ is p-bromobenzyloxycarbonyl; Boc is t-butyloxycarbonyl; and ® is p-methylbenzhydrylamine resin.
 32. The intermediate composition of claim 26 of the formula

    Boc-Tyr(BrZ)-D-Trp-Ala-Trp-D-Phe-Gln-®

wherein BrZ is p-bromobenzyloxycarbonyl; Boc is t-butyloxycarbonyl; and ® is p-methylbenzhydrylamine resin.
 33. The intermediate composition of claim 26 of the formula

    Boc-Tyr(BrZ)-D-Trp-Ala-Trp-D-Phe-Asn-®

wherein BrZ is p-bromobenzyloxycarbonyl; Boc is t-butyloxycarbonyl; and ® is p-methylbenzhydrylamine resin.
 34. The intermediate composition of claim 26 of the formula

    Boc-His(Tos)-D-Trp-Ala-Trp-D-Phe-Lys(ClZ)-®

wherein ClZ is o-chloro-benzyloxycarbonyl; Tos is p-toluenesulfonyl; Boc is t-butyloxycarbonyl; and ® is p-methylbenzhydrylamine resin.
 35. The intermediate composition of claim 26 of the formula

    Boc-Tyr(BrZ)-D-Trp-Ala-Trp-D-His(Tos)-Lys(ClZ)-®

wherein ClZ is o-chloro-benzyloxycarbonyl; Tos is p-toluenesulfonyl; BrZ is p-bromobenzyloxycarbonyl; Boc is t-butyloxycarbonyl; and ® is p-methylbenzhydryalmine resin.
 36. The intermediate composition of claim 26 of the formula

    Boc-Tyr(BrZ)-D-Trp-Ala-Trp-D-Phe-Glu-γ-Bzl-®

wherein γ-Bzl denotes γ-benzyl ester; BrZ is p-bromobenzyloxycarbonyl; Boc is t-butyloxycarbonyl; and ® is p-methylbenzhydrylamine resin.
 37. The intermediate composition of claim 26 of the formula

    Boc-Tyr(BrZ)-D-Trp-Ala-Trp-D-Phe-Phe-®

wherein BrZ is p-bromobenzyloxycarbonyl; Boc is t-butyloxycarbonyl; and ® is p-methylbenzhydrylamine resin.
 38. The intermediate composition of claim 26 of the formula

    Boc-Tyr(BrZ)-D-Trp-Gly-Trp-D-Phe-Gln-ONP-®

wherein ONP is p-nitrophenyl ester; BrZ is p-bromobenzyloxycarbonyl; Boc is t-butyloxycarbonyl; and ® is p-methylbenzhydryalmine resin.
 39. The intermediate composition of claim 26 of the formula

    Boc-His(Tos)-D-Trp-Ala-Trp-D-Phe-Lys(ClZ)-®

wherein ClZ is o-chloro-benzyloxycarbonyl Tos is p-toluenesulfonyl; Boc is t-butyloxycarbonyl; and ® is hydroxymethyl resin.
 40. The intermediate composition of claim 26 of the formula

    Boc-His(Tos)-D-Trp-Ala-Trp-D-Phe-Arg(Tos)-®

wherein Tos is p-toluenesulfonyl; Boc is t-butyloxycarbonyl; and ® is p-methylbenzhydryalmine resin.
 41. The intermediate composition of claim 26 of the formula

    Boc-His(Tos)-D-Trp-Ala-Trp-D-Phe-Gln-ONP-®

wherein ONP is p-nitrophenyl ester; Tos is p-toluenesulfonyl; Boc is t-butyloxycarbonyl; and ® is p-methylbenzhydryalmine resin.
 42. The intermediate composition of claim 26 of the formula

    Boc-His(Tos)-D-Trp-Ala-Trp-D-Phe-Glu-γ-Bzl-®

wherein γ-Bzl denotes γ-benzyl ester; Tos is p-toluenesulfonyl; Boc is t-butyloxycarbonyl; and ® is p-methylbenzhydryalmine resin.
 43. The intermediate composition of claim 26 of the formula

    Boc-His(Tos)-D-Trp-Ala-Trp-D-Phe-HomoArg(Tos)-®

wherein Tos is p-toluenesulfonyl; Boc is t-butyloxycarbonyl; and ® is p-methylbenzhydryalmine resin.
 44. The intermediate composition of claim 26 of the formula

    Boc-3-N-Me-His-D-Trp-Ala-Trp-D-Phe-Lys(ClZ)-®

wherein ClZ is o-chloro-benzyloxycarbonyl; Boc is t-butyloxycarbonyl; and ® is p-methylbenzhydryalmine resin.
 45. The intermediate composition of claim 26 of the formula

    Boc-His(Tos)-D-Trp-Ala-Trp-D-Phe-Lys(ClZ)-®

wherein ClZ is o-chloro-benzyloxycarbonyl; Tos is p-toluenesulfonyl; Boc is t-butyloxycarbonyl; and ® is p-methylbenzhydryalmine resin.
 46. The intermediate composition of claim 26 of the formula

    Boc-His(Tos)-D-Trp-Ala-Trp-D-Phe-Orn(Z)-®

wherein Z is benzyloxycarbonyl; Tos is p-toluenesulfonyl; Boc is t-butyloxycarbonyl; and ® is p-methylbenzhydryalmine resin.
 47. The intermediate composition of claim 26 of the formula

    Boc-His(Tos)-D-Trp-Val-Trp-D-Phe-Lys(ClZ)-®

wherein ClZ is o-chlorobenzyloxycarbonyl; Tos is p-toluenesulfonyl; Boc is t-butyloxycarbonyl; and ® is p-methylbenzhydryalmine resin.
 48. The intermediate composition of claim 26 of the formula

    Boc-His(Tos)-D-Trp-Ser(Bzl)-Trp-D-Phe-Lys(ClZ)-®

wherein ClZ is o-chloro-benzyloxycarbonyl; Bzl is benzyl; Tos is p-toluenesulfonyl; Boc is t-butyloxycarbonyl; and ® is p-methylbenzhydryalmine resin. 